数组 函数
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array_unique

(PHP 4 >= 4.0.1, PHP 5)

array_unique — 移除数组中重复的值

说明

array array_unique ( array $array )

array_unique() 接受 array 作为输入并返回没有重复值的新数组。

注意键名保留不变。array_unique() 先将值作为字符串排序，然后对每个值只保留第一个遇到的键名，接着忽略所有后面的键名。这并不意味着在未排序的 array 中同一个值的第一个出现的键名会被保留。

Note: 当且仅当 (string) $elem1 === (string) $elem2 时两个单元被认为相同。就是说，当字符串的表达一样时。 第一个单元将被保留。

Example #1 array_unique() 例子

<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>

以上例程会输出：

Array
(
    [a] => green
    [0] => red
    [1] => blue
)

Example #2 array_unique() 和类型

<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>

以上例程会输出：

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

参数

array

The input array.

sort_flags

The optional second parameter sort_flags may be used to modify the sorting behavior using these values:

Sorting type flags:

  • SORT_REGULAR - compare items normally (don't change types)
  • SORT_NUMERIC - compare items numerically
  • SORT_STRING - compare items as strings
  • SORT_LOCALE_STRING - compare items as strings, based on the current locale.

返回值

Returns the filtered array.

更新日志

版本 说明
5.2.10 Changed the default value of sort_flags back to SORT_STRING.
5.2.9 Added the optional sort_flags defaulting to SORT_REGULAR. Prior to 5.2.9, this function used to sort the array with SORT_STRING internally.

范例

Example #3 array_unique() example

<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>

以上例程会输出：

Array
(
    [a] => green
    [0] => red
    [1] => blue
)

Example #4 array_unique() and types

<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>

以上例程会输出：

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

参见

注释

Note: Note that array_unique() is not intended to work on multi dimensional arrays.

数组 函数
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PHP手册
PHP手册 - N: 移除数组中重复的值

用户评论:

a dot goergens at web dot de (02-Mar-2012 01:49)

Hi Guys
I got a multidimensional array coming from a database and automatically wanted to push that into a mysql database with all the data and also if possible with realations if the array gets nested. I get the data by a Game via API (ReferenceOutput:
http://wiki.eve-id.net/APIv2_Char_KillLog_XML)
. I am using the Pheal lib which can be found here to access the api and which works fine. https://github.com/ppetermann/pheal

What i want to have is a complete Array2MYSQL  insert and create so the data when it comes from the api is always stored in correct manner 

Anybody can help me?

here are my two functions I tried to use

Rawdata : from the Lib ->http://www.sendspace.com/file/r2cekj
Rawdata  from my Array -> http://www.sendspace.com/file/zg1a32

$table= "corpkills";
$tcounter = "1"  -> in my example
  function array2mysql($array,$table,$tcounter)
 {
  $values = array();
  $fields = array();
  $wert = array();
  $tcounter = $tcounter+1;
      foreach($array as $field =>$value)
      {
              if(is_array($value))
              {
              $fields[] = "`" . $field . "`";
              $values[] = "'" . $value . "'";
              $wert = array2mysql($value,$table,$tcounter);

              }

      $fields[] = "`" . $field . "`";
      $values[] = "'" . $value . "'";
      }

      $field_list = join(',', $fields);
      $value_list = join(', ', $values);
      $query = $wert . "INSERT INTO `" . $table . $tcounter. "` (" . $field_list . ") VALUES (" . $value_list . ");";
      return $query ;
 }

  function array2mysql_create($array,$table,$tcounter)
 {
  $values = array();
  $fields = array();
  $wert = array();
  $tcounter= $tcounter+ 1;
      foreach($array as $field =>$value)
      {
              if(is_array($value))
              {
              $fields[] = "`" . $field . "`varchar (255) NOT NULL";
              $wert = array2mysql_create($value,$table,$tcounter);
              }
              else
              {
              $fields[] = "`" . $field . "`varchar (255) NOT NULL";

              }

      }
      $field_list = join(',', $fields);
      $value_list = join(', ', $values);

      $query = $wert .    "CREATE TABLE `" . $table . $tcounter. "` (id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)," . $field_list . ");";

      return $query ;
 }

gma (at) qoob (dot) gr (12-Nov-2011 06:07)

Lets say that you want to capture unique values from multidimensional arrays and flatten them in 0 depth.

i.e.
<?php
$tmp = array( 'a' => array( 1,2,3,4 ), 'b' => array( 'c' => array( 4,5,6,7 ) ) );
?>

will return with array_flat( $tmp ) --> array( 1,2,3,4,5,6,7 );

I hope that the function will help someone

<?php
/**
 * @params      : $a            array           the recursion array
 *              : $s            array           storage array
 *              : $l            integer         the depth level
 *
 */
if( !function_exists( 'array_flat' ) )
{
    function array_flat( $a, $s = array( ), $l = 0 )
    {
        # check if this is an array
        if( !is_array( $a ) )                           return $s;
       
        # go through the array values
        foreach( $a as $k => $v )
        {
            # check if the contained values are arrays
            if( !is_array( $v ) )
            {
                # store the value
                $s[ ]       = $v;
               
                # move to the next node
                continue;
               
            }
           
            # increment depth level
            $l++;
           
            # replace the content of stored values
            $s              = array_flat( $v, $s, $l );
           
            # decrement depth level
            $l--;
           
        }
       
        # get only unique values
        if( $l == 0 ) $s = array_values( array_unique( $s ) );
       
        # return stored values
        return $s;
       
    } # end of function array_flat( ...
   
}
?>

Friendly Code (01-Aug-2011 11:48)

I required a function that removed a specific duplicate entry from an array and ignoring all others so came up with this:

<?php
function specified_array_unique($array, $value)
{
    $count = 0;
   
    foreach($array as $array_key => $array_value)
    {
        if ( ($count > 0) && ($array_value == $value) )
        {
            unset($array[$array_key]);
        }
       
        if ($array_value == $value) $count++;
    }
   
    return array_filter($array);
}
?>

0cool.f (23-May-2011 11:54)

Hope this can help...

<?php
function array_unique_key_group($array) {
    if(!is_array($array))
        return false;

    $temp = array_unique($array);
    foreach($array as $key => $val) {
        $i = array_search($val,$temp);
        if(!empty($i) && $key != $i) {
            $temp[$i.','.$key] = $temp[$i];
            unset($temp[$i]);
        }
    }
    return $temp;
}
?>

this function return an array that is unique, but preserve every key for the element...
sorry for bad english I'm italian...

$array['asd'] = 'value';
$array['lol'] = 'value';
$array['foo'] = 'val';
$array['bar'] = 'val';

var_dump(array_unique_key_group($array));
// will be output
array(2) { ["asd,lol"]=> string(5) "value" ["foo,bar"]=> string(3) "val" }

mykelscappin at gmail dot com (31-Mar-2011 01:18)

I made an array_unique function to handle deep arrays:

<?php
    function array_unique_deep($array) {
        $values=array();
        //ideally there would be some is_array() testing for $array here...
        foreach ($array as $part) {
            if (is_array($part)) $values=array_merge($values,array_unique_deep($part));
            else $values[]=$part;
        }
        return array_unique($values);
    }
   
    $test=array(123,456,array(789,123,array(456),789),array(123));
    print_r(array_unique_deep($test));
   
?>

outputs

Array
(
    [0] => 123
    [1] => 456
    [2] => 789
)

simon (11-Oct-2010 01:01)

if you want to close the gaps into the keys after using array_unique() you can use array_values() afterwards. Example:

<?php
a = array("one", "two", "two", "three")
a = array_unique(a);
/* will lead to:
a[0] = "one"
a[1] = "two"
a[3] = "three"
*/
a = array_values(a);
/* Now we've got:
a[0] = "one"
a[1] = "two"
a[2] = "three"
*/
?>

michiel ed thalent nl (19-Jun-2010 01:04)

If you use SORT_NUMERIC on this kind of filtering it will be significantly faster.
However the array_flip method still is twice as fast.

Anonymous (16-Jun-2010 01:46)

It's often faster to use a foreache and array_keys than array_unique:

    <?php

    $max = 1000000;
    $arr = range(1,$max,3);
    $arr2 = range(1,$max,2);
    $arr = array_merge($arr,$arr2);

    $time = -microtime(true);
    $res1 = array_unique($arr);
    $time += microtime(true);
    echo "deduped to ".count($res1)." in ".$time;
    // deduped to 666667 in 32.300781965256

    $time = -microtime(true);
    $res2 = array();
    foreach($arr as $key=>$val) {   
        $res2[$val] = true;
    }
    $res2 = array_keys($res2);
    $time += microtime(true);
    echo "<br />deduped to ".count($res2)." in ".$time;
    // deduped to 666667 in 0.84372591972351

    ?>

regeda at inbox dot ru (12-Apr-2010 04:11)

recursive array unique for multiarrays

<?php
function super_unique($array)
{
  $result = array_map("unserialize", array_unique(array_map("serialize", $array)));

  foreach ($result as $key => $value)
  {
    if ( is_array($value) )
    {
      $result[$key] = super_unique($value);
    }
  }

  return $result;
}
?>

brendel at krumedia dot de (24-Feb-2010 07:47)

Prior to 5.2.9 you may create a list of unique objects this way:

<?php
for (; ; ) {
  // ...
  $uniqueObjectList[spl_object_hash($myObject)] = $myObject;
}
?>

amri [ at t] dhstudio dot eu (18-Dec-2009 10:36)

I searched how to show only the duplicate elements from array, but failed.
Here is my solution:

<?php
function arrayDuplicate($array)
{
return array_unique(array_diff_assoc($array1,array_unique($array1)));
};
?>

Example:
<?php
$arr1 = array('foo', 'bar', 'xyzzy', '&', 'xyzzy',
'baz', 'bat', '|', 'xyzzy', 'plugh',
'xyzzy', 'foobar', '|', 'plonk', 'xyzzy',
'apples', '&', 'xyzzy', 'oranges', 'xyzzy',
'pears','foobar');

$result=arrayDuplicate($arr1);
print_r($result);exit;
?>

Output:

Array
(
[4] => xyzzy
[12] => |
[16] => &
[21] => foobar
)

Youssef Omar (16-Dec-2009 07:09)

This is how to merge 2 comma separated lists with unique value only.

<?php
  $list1 = "4444, 5555, 6666";
  $list2 = "4444, 5555, 7777";

  // combine both lists with unique values only
  $list3 = implode("," , array_unique(array_merge(explode(",",$list1),explode(",", $list2))));

  echo $list3;
?>

The result is: 4444,5555,6666,7777

macnimble at gmail dot com (08-Sep-2009 04:24)

I'm not sure why you'd use any kind of loop to get the duplicates in an array. Here's a handy little function which does exactly that using some of PHP's other array_* functions.

<?php
function array_not_unique( $a = array() )
{
  return array_diff_key( $a , array_unique( $a ) );
}
?>

Some arrays for testing:

<?php
$person = array();
$person[1] = "person_1";
$person[2] = "person_2";
$person[3] = "person_3";
$person[4] = "person_4";
$person[5] = "person_5";
$person[6] = "person_2"; # DUPE
$person[7] = "person_4"; # DUPE
$person[8] = "person_4"; # DUPE
echo '<pre>',print_r(array_not_unique($person),1),'</pre>';
$person = array();
$person[] = 1;
$person[] = 2;
$person[] = 3;
$person[] = 4;
$person[] = 5;
$person[] = 2; # DUPE
$person[] = 4; # DUPE
$person[] = 4; # DUPE
echo '<pre>',print_r(array_not_unique($person),1),'</pre>';
?>

Output:
Array
(
    [6] => person_2
    [7] => person_4
    [8] => person_4
)

Array
(
    [5] => 2
    [6] => 4
    [7] => 4
)

Hope it helps.
--Bill

steve at visual77 dot com (27-May-2009 12:41)

One way to use array_unique() to handle the multidimensional array issue is to use an md5 hash of the serialized array as the key. I've seen some solutions listed here that stored the serialized string, but that requires unserialization, and moving data back and forth between two states for little reason is just a bad idea. Instead, you could try this method:

<?php
$values = array();

foreach($data as $d) {
    $values[md5(serialize($d))] = $d;
}

sort($values);
?>

This will serialize and hash the value, and store the value with the hash as they key. This will ensure that each piece is only stored once, as the second attempt to store will just overwrite the first attempt with identical data.

The sort() at the end is a bit unnecessary, but I had to use it on my project, because the function I was passing the array to couldn't handle keys that weren't valid XML node names (and some md5 hash strings will start with numbers, which is invalid for XML).

dirk dot avery a t gmail (30-Apr-2009 04:45)

Although array_unique is not intended to work with multi-dimensional arrays, it does on 5.2.9.  However, it does not for 5.2.5.  Beware.

Ultimater at gmail dot com (21-Apr-2009 02:26)

Let's say you have
<?php
$v=array("blue","blue","blue","blue");
if($v[0]==$v[1] && $v[1]==$v[2] && $v[2]==$v[3])
echo "Y"; else echo "N";//Y
?>

It works but the if-statement gets a bit messy if the number of array elements gets massive.
I find it is easier to use array_unique like so:
<?php
$v=array("blue","blue","blue","blue");
echo sizeof(array_unique($v))==1?"Y":"N";//Y
?>

inithello at gmail dot com (12-Mar-2009 07:47)

I noticed there was no way to tell array_unique() to ignore certain duplicated keys, so I wrote the following. I imagine there's half a dozen more efficient ways to do this, but here goes:

<?php
$array = array('foo', 'bar', 'xyzzy', '&', 'xyzzy',
               'baz', 'bat', '|', 'xyzzy', 'plugh',
               'xyzzy', 'foobar', '|', 'plonk', 'xyzzy',
               'apples', '&', 'xyzzy', 'oranges', 'xyzzy',
               'pears');

$ignore_values = array('|', '&');

print_r(make_unique($array, $ignore_values));

function make_unique($array, $ignore)
{
    while($values = each($array))
    {
        if(!in_array($values[1], $ignore))
        {
            $dupes = array_keys($array, $values[1]);
            unset($dupes[0]);
            foreach($dupes as $rmv)
            {
                unset($array[$rmv]);
            }           
        }
    }
    return $array;
}
?>
OUTPUT:
Array
(
    [0] => foo
    [1] => bar
    [2] => xyzzy
    [3] => &
    [5] => baz
    [6] => bat
    [7] => |
    [9] => plugh
    [11] => foobar
    [12] => |
    [13] => plonk
    [15] => apples
    [16] => &
    [18] => oranges
    [20] => pears
)

serg dot podtynnyi at gmail dot com (06-Feb-2009 07:21)

//Remove duplicates from a text files and dump result in one file for example: emails list, links list etc

<?php

$data1 = file("data1.txt");
$data2 = file("data2.txt");

file_put_contents('unique.txt', implode('', array_unique(array_merge($data1,$data2))));
?>

jusvalceanu - SPAM at SPAM - yahoo dot com (06-Nov-2008 10:23)

so .... my problem was multidimensional sort.

<?php
      $new = array();
      $exclude = array("");
      for ($i = 0; $i<=count($attribs)-1; $i++) {
         if (!in_array(trim($attribs[$i]["price"]) ,$exclude)) { $new[] = $attribs[$i]; $exclude[] = trim($attribs[$i]["price"]); }
      }

?>

Array $attribs is an array contaning arrays. Each array in the $attrib array consists in multiple fields (ex: name, lenght, price, etc.) to be more simpler in speech think that $attrib is the array resulted by a search sql query done by a visitator on your online shoopping website ... (so ... each array in the $attrib is a product :P) if you want to sort only the uniq results use the above or use this:

<?php
 
   /* Our Array of products */
   $attribs[] = array(
                           "name"         => "Test Product 1",
                           "length"     => "42 cm",
                           "weight"     => "0,5 kg",
                           "price"     => "10 $",
                           "stock"     => "100",
                        );

   $attribs[] = array(
                           "name"         => "Test Product 2",
                           "length"     => "42 cm",
                           "weight"     => "1,5 kg",
                           "price"     => "10 $",
                           "stock"     => "200",
                        );

    /* The nice stuff */

      $new = array();
      $exclude = array("");
      for ($i = 0; $i<=count($attribs)-1; $i++) {
         if (!in_array(trim($attribs[$i]["price"]) ,$exclude)) { $new[] = $attribs[$i]; $exclude[] = trim($attribs[$i]["price"]); }
      }
     
      print_r($new); // $new is our sorted array

?>

Have fun tweaking this ;)) i know you will ;))

From Romania With Love

florian at box dot net (08-Oct-2008 09:29)

I came across one limitation of array_unique: it doesn't work properly if you have arrays inside your main array.

The reason is that to compare two values, the function tests if (string) $value1 == (string) $value2. So if $value1 and $value2 are both arrays, the function will evaluate the test to 'Array' == 'Array', and decide that the $values are repeated even if the arrays are different.

So a work around is to find a better conversion of an array to a string, which can be done with json:

<?php
print "define an array with repeated scalar '1' and repeated 'array(1)':";
$a_not_unique = array(
    'a' => 1,
    'b' => 1,
    'c' => 2,
    'd' => array(1),
    'e' => array(1),
    'f' => array(2),
);
print_r($a_not_unique);

print "try to use simply array_unique, which will not work since it exludes 'array(2)':";
$a_unique_wrong = array_unique($a_not_unique);
print_r($a_unique_wrong);

print "convert to json before applying array_unique, and convert back to array, which will successfully keep 'array(2)':";
$a_unique_right = $a_not_unique;
array_walk($a_unique_right, create_function('&$value,$key', '$value = json_encode($value);'));
$a_unique_right = array_unique($a_unique_right);
array_walk($a_unique_right, create_function('&$value,$key', '$value = json_decode($value, true);'));
print_r($a_unique_right);
?>

Results:
define an array with repeated scalar '1' and repeated 'array(1)':
Array
(
    [a] => 1
    [b] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )

    [e] => Array
        (
            [0] => 1
        )

    [f] => Array
        (
            [0] => 2
        )
)

try to use simply array_unique, which will not work since it exludes 'array(2)':
Array
(
    [a] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )
)

convert to json before applying array_unique, and convert back to array, which will successfully keep 'array(2)':
Array
(
    [a] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )

    [f] => Array
        (
            [0] => 2
        )
)

quecoder at gmail (26-Aug-2008 06:30)

another method to get unique values is :

<?php
$alpha=array('a','b','c','a','b','d','e','f','f');

$alpha= array_keys(array_count_values($alpha));

print_r($alpha);
?>

Output:
Array ( [0] => a [1] => b [2] => c [3] => d [4] => e [5] => f )

soapergem at gmail dot com (14-Aug-2008 10:39)

Here's another solution for returning an array that only includes repeated values. There is one given below but it only works on numerically indexed arrays; this one is more comprehensive since I used the foreach iterator. Also, this one preserves keys--in that the returned result contains a distinct list of repeats (storing only the first instance it encounters of each duplicate value).

<?php

function array_repeated($array)
{
    if ( !is_array($array) ) {
        return false;
    }
   
    $duplicates = array();
    foreach ( $array as $key => $val ) {
        end($array);
        $k = key($array);
        $v = current($array);
       
        while ( $k !== $key ) {
            if ( $v === $val ) {
                $duplicates[$key] = $v;
                                break;
            }
           
            $v = prev($array);
            $k = key($array);
        }
    }
   
    return $duplicates;
}

?>

Dorphalsig (28-Jul-2008 05:47)

I had a problem with array_unique and multidimensional arrays ... Maybe there's a better way to do this, but this will work for any dimensional arrays.

<?php
function arrayUnique($myArray)
{
    if(!is_array($myArray))
           return $myArray;

    foreach ($myArray as &$myvalue){
        $myvalue=serialize($myvalue);
    }

    $myArray=array_unique($myArray);

    foreach ($myArray as &$myvalue){
        $myvalue=unserialize($myvalue);
    }

    return $myArray;

}
?>

ali at zkurd dot org (19-Jun-2008 09:41)

a lot of people create functions just to fix a notice error about an undefined index and removes blank array value.

why not using foreach instead of the for loop?

example:
<?php
foreach ($arrayname as $key => $value) {
    //do what you want with $value withaout index stress
}
?>

PHP Expert (14-Apr-2008 01:34)

case insensitive for PHP v4.x and up.

<?php

function in_iarray($str, $a){
foreach($a as $v){
if(strcasecmp($str, $v)==0){return true;}
}
return false;
}

function array_iunique($a){
$n = array();
foreach($a as $k=>$v){
if(!in_iarray($v, $n)){$n[$k]=$v;}
}
return $n;
}

$input = array("aAa","bBb","cCc","AaA","ccC","ccc","CCC","bBB","AAA","XXX");
$result = array_iunique($input);
print_r($result);

/*
Array
(
    [0] => aAa
    [1] => bBb
    [2] => cCc
    [9] => XXX
)
*/
?>

Ray dot Paseur at SometimesUsesGmail dot com (02-Mar-2008 03:46)

I needed to identify email addresses in a data table that were replicated, so I wrote the array_not_unique() function:

<?php

function array_not_unique($raw_array) {
    $dupes = array();
    natcasesort($raw_array);
    reset ($raw_array);

    $old_key    = NULL;
    $old_value    = NULL;
    foreach ($raw_array as $key => $value) {
        if ($value === NULL) { continue; }
        if ($old_value == $value) {
            $dupes[$old_key]    = $old_value;
            $dupes[$key]        = $value;
        }
        $old_value    = $value;
        $old_key    = $key;
    }
return $dupes;
}

$raw_array     = array();
$raw_array[1]    = 'abc@xyz.com';
$raw_array[2]    = 'def@xyz.com';
$raw_array[3]    = 'ghi@xyz.com';
$raw_array[4]    = 'abc@xyz.com'; // Duplicate

$common_stuff    = array_not_unique($raw_array);
var_dump($common_stuff);
?>

php_array_unique [at] peterwarnock.com (19-Dec-2007 07:20)

To clarify the note above Example #1, the function appears to cast the elements to strings for comparison and then return the type of the first unique element encountered. 

<?php
$input = array(0, 2, "2", 3, "9", 9);
$result = array_unique($input);
var_dump($result);
?>

array(4) {
  [0]=>
  int(0)
  [1]=>
  int(2)
  [3]=>
  int(3)
  [4]=>
  string(1) "9"
}

mnbayazit (28-Oct-2007 10:18)

case insensitive

<?php
function array_iunique($array) {
    return array_intersect_key($array,array_unique(
                 array_map(strtolower,$array)));
}
?>

xjazey at hotmail dot com (11-Sep-2007 07:50)

This is a solution to remove duplicate values from an array

<?php

$array[0] = "Yellow";
$array[1] = "Green";
$array[2] = "Yellow";
$array[3] = "Blue";
$array[4] = "Yellow";

$array = array_keys(array_flip($array));

//$array will output Yellow Green Blue

?>

tsikano at attglobal dot net (22-Aug-2007 12:20)

Suggestion for being able to use array_unique on array of arrays/objects:

<?php
foreach ($arrayOfArrays as $key=>$value) {
  $arrayOfArrays[$key] = "'" . serialize($value) . "'";
}
$arrayOfArrays = array_unique($arrayOfArrays);
foreach ($arrayOfArrays as $key=>$value) {
  $arrayOfArrays[$key] = unserialize(trim($value, "'"));
}
?>

webmaster at jukkis dot net (30-Jul-2007 12:08)

Another way to 'unique column' an array, in this case an array of objects:
Keep the desired unique column values in a static array inside the callback function for array_filter.

Example:
<?php
/* example object */
class myObj {
  public $id;
  public $value;
  function __construct( $id, $value ) {
    $this->id = $id;
    $this->value = $value;
  }
}

/* callback function */
function uniquecol( $obj ) {
  static $idlist = array();

  if ( in_array( $obj->id, $idlist ) )
    return false;

  $idlist[] = $obj->id;
  return true;   
}

/* a couple of arrays with second array having an element with same id as the first */
$list  = array( new myObj( 1, 1  ), new myObj( 2, 100 ) );
$list2 = array( new myObj( 1, 10 ), new myObj( 3, 100 ) );
$list3 = array_merge( $list, $list2 );

$unique = array_filter( $list3, 'uniquecol' );
print_r( $list3 );
print_r( $unique );

?>

In addition, use array_merge( $unique ) to reindex.

arr1 (01-Nov-2006 04:59)

Just to note that array_unique, treats null values as none unique values. So if your using array_unique to detect duplicate values it will also detect multiple null values.

Ome_Henk (27-Oct-2006 08:16)

For people looking at the flip flip method for getting unique values in a simple array. This is the absolute fastest method:

<?php
$unique = array_keys(array_flip($array));
?>

It's marginally faster as:
<?php
$unique = array_merge(array_flip(array_flip($array)));
?>

And it's marginally slower as:
<?php
$unique array_flip(array_flip($array)); // leaves gaps
?>

It's still about twice as fast or fast as array_unique.

This tested on several different machines with 100000 random arrays. All machines used a version of PHP5.

geuis dot teses at gmail dot com (09-Oct-2006 06:27)

Here's the shortest line of code I could find/create to remove all duplicate entries from an array and then reindex the keys.

<?php

// Fruits, vegetables, and other food:
$var = array('apple','banana','carrot','cat','dog','egg','eggplant','fish');

$var = array_values(array_unique($var));
?>

keneks at gmail dot com (30-Sep-2006 03:01)

Taking the advantage of array_unique, here is a simple function to check if an array has duplicate values.

It simply compares the number of elements between the original array and the array_uniqued array.

<?php
function array_search_dups($array)
{
    $dup_array = $array;
    $dup_array = array_unique($dup_array);
    if(count($dup_array) != count($array))
    {
        return TRUE;
    }
    else
    {
        return FALSE;
    }
}
?>

pulsarkowy at NOSPAM dot gmail dot com (13-Sep-2006 12:30)

This function below will remove multiple values from array, remove 'empty' fields an also count how many times the given value occured.

it's rather slow and not 'elegant' but works.

usage:
<?php
$myarray = my_array_unique($myarray);
?>

in return it produces an 3 fields array:
1st is index number, 2nd is the value, 3rd is counter.

<?php
function my_array_unique($tablica)
{

$tnum=count($tablica);
$i=1;
$k=1;
$t[1]['product']="";
$t[1]['count']=1;
while($i<=$tnum) {
  if (!array_multi_search($tablica[$i], $t)) {
    $t[$k]['product']=$tablica[$i];
    $t[$k]['count']=1;
    $k++;
  }
  else {
    $y=1;
    while ($y<=count($t)) {
      if ($t[$y]['product']==$tablica[$i])
        $t[$y]['count']++;
      $y++;
    }

  }
 
$i++;
} 

$tablica=$t;
return $tablica;
}
?>

the function uses another function that i've found on the php.net site (i'm posting it only for informational reasons - i can't remember who wrote it):

<?php
function array_multi_search( $p_needle, $p_haystack )
   {
       if( !is_array( $p_haystack ) )
       {
           return false;
       }

       if( in_array( $p_needle, $p_haystack ) )
       {
           return true;
       }

       foreach( $p_haystack as $row )
       {
           if( array_multi_search( $p_needle, $row ) )
           {
               return true;
           }
       }

       return false;
   }
?>

[EDIT BY danbrown AT php DOT net: The array_multi_search() function was originally written by 'czeslaw' and posted to the in_array() function manual entry on 18 February, 2006.]

uditsawhney at yahoo dot com (15-Jul-2006 08:14)

<?php

//Fn for array_unique column-wise for multi-dimensioanl array without losing keys | Start
function array_uniquecolumn($arr)
{
    $rows   = sizeof($arr);
    $columns = sizeof($arr[0]);
   
    $columnkeys = array_keys($arr[0]);
   

    for($i=0; $i<$columns; $i++)
    {
        for($j=0;$j<$rows;$j++)
        {
            for($k = $j+1; $k<$rows; $k++)
            {
                if($arr[$j][$columnkeys[$i]] == $arr[$k][$columnkeys[$i]])
                    $arr[$k][$columnkeys[$i]] = "";       
            }
        }
   
    }

return ($arr);

}
//Fn for array_unique column-wise for multi-dimensioanl array without losing keys | Stop

$arrUGCourse[]= array(  "CTR" => "1",

                        "UGCOURSE"=>"ABC",

                        "TSINITIATE"=>"540",

                        "COUNT"=>"34",

                        "ENTRY_DT"=>"2006-05-01",

                        "CUMULATIVE"=> 44);

 

$arrUGCourse[]= array(  "CTR" => "2",

                        "UGCOURSE"=>"ABC",

                        "TSINITIATE"=>"5401",

                        "COUNT"=>"341",

                        "ENTRY_DT"=>"2006-05-11",

                        "CUMULATIVE"=> 44);

print_r(array_uniquecolumn($arrUGCourse));

?>

MoD (14-Apr-2006 05:02)

The shortest way i found to remove duplicate array from a column,
For example if you parse Multiple XML sources, you can remove duplicate items that contain the same link.

<?PHP
function        remove_duplicate($array, $field)
{
  foreach ($array as $sub)
    $cmp[] = $sub[$field];
  $unique = array_unique($cmp);
  foreach ($unique as $k => $rien)
    $new[] = $array[$k];
  return $new;
}
?>

agarcia at rsn dot com dot co (31-Mar-2006 08:41)

This is a script for multi_dimensional arrays

<?php
function remove_dup($matriz) {
    $aux_ini=array();
    $entrega=array();
    for($n=0;$n<count($matriz);$n++)
    {
        $aux_ini[]=serialize($matriz[$n]);
    }
    $mat=array_unique($aux_ini);
    for($n=0;$n<count($matriz);$n++)
    {
       
            $entrega[]=unserialize($mat[$n]);
       
    }
    return $entrega;
}
?>

mcmeijer at yahoo dot com (27-Jan-2006 01:18)

This is a recursive arrayUnique function for arrays of any dimension. (tested with 4-dimensional array)
The line '$newArray=deleteEmpty($newArray);' is optional and removes empty keys and values
<?php
function arrayUnique($myArray)
    {
    $newArray = Array();
    if (is_array($myArray))
        {
        foreach($myArray as $key=>$val)
            {
            if (is_array($val))
                {
                $val2 = arrayUnique($val);
                }
            else
                {
                $val2 = $val;
                $newArray=array_unique($myArray);
                $newArray=deleteEmpty($newArray);
                break;
                }
            if (!empty($val2))
                {
                $newArray[$key] = $val2;
                }
            }
        }
    return ($newArray);
    }

function deleteEmpty($myArray)
    {
    $retArray= Array();
    foreach($myArray as $key=>$val)
        {
        if (($key<>"") && ($val<>""))
            {
            $retArray[$key] = $val;
            }
        }
    return $retArray;
    }
?>

memandeemail at gmail dot com (03-Jan-2006 06:47)

Problem:
I have loaded an array with the results of a database
query.  The Fields are 'FirstName' and 'LastName'.

I would like to find a way to contactenate the two
fields, and then return only unique values for the
array.  For example, if the database query returns
three instances of a record with the FirstName John
and the LastName Smith in two distinct fields, I would
like to build a new array that would contain all the
original fields, but with John Smith in it only once.
Thanks for: Colin Campbell

Solution:

<?php
/**
 * The same thing than implode function, but return the keys so
 *
 * <code>
 * $_GET = array('id' => '4587','with' => 'key');
 * ...
 * echo shared::implode_with_key('&',$_GET,'='); // Resultado: id=4587&with=key
 * ...
 * </code>
 *
 * @param string $glue Oque colocar entre as chave => valor
 * @param array $pieces Valores
 * @param string $hifen Separar chave da array do valor
 * @return string
 * @author memandeemail at gmail dot com
 */
function implode_with_key($glue = null, $pieces, $hifen = ',') {
  $return = null;
  foreach ($pieces as $tk => $tv) $return .= $glue.$tk.$hifen.$tv;
  return substr($return,1);
}

/**
 * Return unique values from a tree of values
 *
 * @param array $array_tree
 * @return array
 * @author memandeemail at gmail dot com
 */
function array_unique_tree($array_tree) {
  $will_return = array(); $vtemp = array();
  foreach ($array_tree as $tkey => $tvalue) $vtemp[$tkey] = implode_with_key('&',$tvalue,'=');
  foreach (array_keys(array_unique($vtemp)) as $tvalue) $will_return[$tvalue] = $array_tree[$tvalue];
  return $will_return;
}

$problem = array_fill(0,3,
array('FirstName' => 'John', 'LastName' => 'Smith')
);

$problem[] = array('FirstName' => 'Davi', 'LastName' => 'S. Mesquita');
$problem[] = array('FirstName' => 'John', 'LastName' => 'Tom');

print_r($problem);

print_r(array_unique_tree($problem));
?>

webcreator at centrum dot cz (28-Oct-2005 12:25)

array_unique function starts its comparation from beginning and pop the key off if there is more values inside array. The last one remains. But i needed to hold priority of the order of values and let the first one in.

Here is my easy solution:

<?php
function my_array_unique($from)
{
for ($i=count($from);$i>1;$i--)
    {
    $last = $from[$i];
    $from[$i] = "";
    if (!in_array($last,$from))
        $from[$i]=$last;   
    }
return array_unique($from);
}

# One empty value remains in array.
# But its very easy to separate it while using output array.
?>

passtschu AT freenet DOT de (21-Sep-2005 03:20)

array_unique for multidimensional arrays. similar to the DISTINCT in SQL function.
the function can group, sum and count keys

<?PHP
/*
$array - nothing to say
$group_keys - columns which have to be grouped - can be STRING or ARRAY (STRING, STRING[, ...])
$sum_keys - columns which have to be summed - can be STRING or ARRAY (STRING, STRING[, ...])
$count_key - must be STRING - count the grouped keys
*/
function array_distinct ($array, $group_keys, $sum_keys = NULL, $count_key = NULL){
  if (!is_array ($group_keys)) $group_keys = array ($group_keys);
  if (!is_array ($sum_keys)) $sum_keys = array ($sum_keys);

  $existing_sub_keys = array ();
  $output = array ();

  foreach ($array as $key => $sub_array){
    $puffer = NULL;
    #group keys
    foreach ($group_keys as $group_key){
      $puffer .= $sub_array[$group_key];
    }
    $puffer = serialize ($puffer);
    if (!in_array ($puffer, $existing_sub_keys)){
      $existing_sub_keys[$key] = $puffer;
      $output[$key] = $sub_array;
    }
    else{
      $puffer = array_search ($puffer, $existing_sub_keys);
      #sum keys
      foreach ($sum_keys as $sum_key){
        if (is_string ($sum_key)) $output[$puffer][$sum_key] += $sub_array[$sum_key];
      }
      #count grouped keys
      if (!array_key_exists ($count_key, $output[$puffer])) $output[$puffer][$count_key] = 1;
      if (is_string ($count_key)) $output[$puffer][$count_key]++;
    }
  }
  return $output;
}
?>

muddmonkey@harveyMcoldotedu (17-Aug-2005 09:44)

If you're doing numeric arrays etc. I found flip-flip to work much better than array_unique:

<?PHP
    function microtime_float(){ //timing
       list($usec, $sec) = explode(" ", microtime());
       return ((float)$usec + (float)$sec);
    }

    //make an arry and fill it up
    $final=array();
    for($i=0;$i<50000;$i++){
        $final[]=$i%13; //make sure there are some dupes
    }
    //try array unique
    $start1 = microtime_float();
    array_unique($final);
    $stop1=microtime_float();
    echo($stop1-$start1.'<br>');
    //try my flip-flip
    $start2=microtime_float();
    array_flip(array_flip($final));
    $stop2=microtime_float();
    echo($stop2-$start2);
?>

Running this with only ints in the array (as above) I get runtimes such as:
1.6195669174194 (using unique)
0.017037868499756 (using flip flip)
which is two orders of magnitude faster!

Appending a string:
($final[]='test'.$i%13;)
gives:
0.42909598350525 (using unique)
0.023258924484253 (using flip-flip)
Which is not AS great, but still 20x faster than unique.

In both cases the flip-flip seems to use less memory than the unique.

Granted the flip-flip doesn't work for all cases, but if you're doing simple stuff like this, the flip-flip will give you better run times.

~JF

Christoph Ziegenberg (17-Jun-2005 07:44)

If the array key is a string it might be important to keep it although the value is the same (as I need it at the moment). So I wrote a function which also returns array elements which have the same value but different string keys.

<?php
function array_unique_numeric ($arr)
{
    $str = $int = array();
    foreach(array_keys($arr) as $key) {
        ${(is_int($key)?'int':'str')}[$key] = $arr[$key];
    }
    return array_merge($str, array_unique($int));
}

// typical array after an array_merge()...
$array = array("a" => "green", "b" => "brown", "c" => "blue", "red", "d" => "green", "yellow", "red");

print_r(array_unique($array));
// Array
// (
//     [a] => green
//     [b] => brown
//     [c] => blue
//     [0] => red
//     [1] => yellow
// )

print_r(array_unique_numeric($array));
// Array
// (
//     [a] => green
//     [b] => brown
//     [c] => blue
//     [d] => green
//     [0] => red
//     [1] => yellow
// )
?>

memandeemail at gmail dot com (15-Apr-2005 09:46)

<?php
/**
 * Removes duplicate keys from an array
 *
 * @param array $array
 * @return array
 */
function array_unique_key($array) {
    $result = array();
    foreach (array_unique(array_keys($array)) as $tvalue) {
        $result[$tvalue] = $array[$tvalue];
    }
    return $result;
}
?>

Ric (05-Apr-2005 05:44)

A very simple way of getting rid of duplicate entries and re-indexing with key starting at 0:

<?php
    $temp=array_unique($main);
    $main=array_values($temp);
?>

trigger at e-mail dot ru (03-Feb-2005 10:53)

Just a simple implementation for JavaScript:

<?php
function array_unique(thearray)
{
    thearray.sort();
    //reset($thearray);
    newarray = new Array();
    for (n=0;n<thearray.length;n++)
    {
        unique=1;//by default
        for(nn=0;nn<newarray.length;nn++)
            if (thearray[n] == newarray[nn])
            {
                unique=0;//already exists
                break;
            }
        if(unique)//dont exists
            newarray.push(thearray[n]);
    }
    return newarray;
 }
?>

lucas.bickel AT purplehaze DOT ch (26-Oct-2004 04:39)

I quite like the following code for making multidimensional arrays unique:

<?php
foreach ($arrAddressList AS $key => $arrAddress) {
    $arrAddressList[$key] = serialize($arrAddress);
}
$arrAddressList = array_unique($arrAdressList);
foreach ($arrAddressList AS $key => $strAddress) {
    $arrAddressList[$key] = unserialize($strAddress);
}
?>

This gets me a unique array while not minding wether the the original array contains arrays or just strings (or whatever...).

wernerlistas at terra dot com dot br (16-Jun-2004 04:50)

Following the code copies of a little function I've wrote that actually works with multidimensional arrays.
It also resets the array indexes.

<?php
if ( !function_exists( "arrayUnique" ) ){
    function arrayUnique ( $rArray ){
        $rReturn = array ();
        while ( list( $key, $val ) = each ( $rArray ) ){
            if ( !in_array( $val, $rReturn ) )
            array_push( $rReturn, $val );
        }
        return $rReturn;
    }
}
?>

csaba at alum dot mit dot edu (10-Jun-2004 03:17)

The following is an efficient, adaptable implementation of array_unique which always retains the first key having a given value:

<?php
function array_unique2(&$aray) {
    $aHash = array();
    foreach ($aray as $key => &$val) if (@$aHash[$val]++) unset ($aray[$key]);
}
?>

It is also adaptable to multi dimensional arrays.  For example, if your array is a sequence of (multidimensional) points, then in place of @$aHash[$val]++ you could use @$aHash[implode("X",$val)]++
If you want to not have holes in your array, you can do an array_merge($aray) at the end.

Csaba Gabor

patrikG at home dot net (11-Mar-2004 03:05)

If you need to have the keys of the duplicates in an array returned, you may find this function useful:

<?php
function unique_events($array){
    //checks $array for duplicate values and returns an
        //array containing the keys of duplicates
    $count= array_intersect_assoc($array, array_flip( array_count_values($array)));
    foreach($array as $key=>$value){
        if (in_array($value,$count)){
            $return[$value][]=$key;
        }
    }
    return $return;
}
?>

Example:

Input:
Array
(
    [0] => 44
    [1] => 23
    [2] => 23
    [3] => 23
    [4] => 9
    [5] => 9
    [6] => 9
    [7] => 9
    [8] => 9
    [9] => 9
    [10] => 9
    [11] => 9
)

Function returns:
Array
(
    [23] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )

    [9] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
            [3] => 7
            [4] => 8
            [5] => 9
            [6] => 10
            [7] => 11
        )

)

bitmore.co.kr (19-Feb-2004 11:53)

//Modify
Object Unique

<?php
    class foo {
        var $_name;
        var $_age;
        function foo($name,$age=NULL)    { $this->_name = $name; $this->_age = $age; }
        //function get()        { return $this->_name; }
        //function set($name,$age=NULL)    { $this->_name = $name; $this->_age = $age; }
    }

    function DistinctOn ($obj, $item) {
        $out = array();
        $list = array();
        foreach ($obj as $key=>$so) {
            if (!in_array($so->$item, $list)) {
                echo "key = $key,so = $so,item = $item,IFlist = ";print_r($list);echo "<br>";
                $list[] = $so->$item;//迭
                $out[$key] = $so;
            }
            echo "Forlist = ";print_r($list);echo "<br>";
        }
        return $out;
    }

    $foo_obj[0] = new foo('tom',20);
    $foo_obj[1] = new foo('paul',66);
    $foo_obj[2] = new foo('tom',23);

    $item = '_name';
    $result = DistinctOn ($foo_obj, $item);

    while(list($k,$v) = each($result)) {
        print "K = ";print_r($k);
        print ",V = ";print_r($v);
        print "<br>";
    }
    //key = 0,so = Object,item = _name,IFlist = Array ( ) ,Forlist = Array ( [0] => tom )
    //key = 1,so = Object,item = _name,IFlist = Array ( [0] => tom ) ,Forlist = Array ( [0] => tom [1] => paul )
    //Forlist = Array ( [0] => tom [1] => paul )
    //K = 0,V = foo Object ( [_name] => tom [_age] => 20 )
    //K = 1,V = foo Object ( [_name] => paul [_age] => 66 )

    print "<br><br>";
    $item = '_age';
    $result = DistinctOn ($foo_obj, $item);
    while(list($k,$v) = each($result)) {
        print "K = ";print_r($k);
        print ",V = ";print_r($v);
        print "<br>";
    }

    //key = 0,so = Object,item = _age,IFlist = Array ( ) ,Forlist = Array ( [0] => 20 )
    //key = 1,so = Object,item = _age,IFlist = Array ( [0] => 20 ) ,Forlist = Array ( [0] => 20 [1] => 66 )
    //key = 2,so = Object,item = _age,IFlist = Array ( [0] => 20 [1] => 66 ) ,
    //    Forlist = Array ( [0] => 20 [1] => 66 [2] => 23 )
    //K = 0,V = foo Object ( [_name] => tom [_age] => 20 )
    //K = 1,V = foo Object ( [_name] => paul [_age] => 66 )
    //K = 2,V = foo Object ( [_name] => tom [_age] => 23 )
?>

kay_rules at yahoo dot com (24-May-2003 10:28)

this function will return an array with unique value and proper key increment start from 0.

<?php
/*******************************/
function my_array_unique($somearray){
    $tmparr = array_unique($somearray);
    $i=0;
    foreach ($tmparr as $v) {
        $newarr[$i] = $v;
        $i++;
    }
    return $newarr;
}
/********************************/
?>

eg:

<?php
$foo_arr[0] ='aa'
$foo_arr[1] ='bb'
$foo_arr[2] ='cc'
$foo_arr[3] ='bb'
$foo_arr[4] ='aa'
$foo_arr[5] ='dd'
?>

normal array_unique will return:

<?php
$foo_arr[0] ='aa';
$foo_arr[1] ='bb';
$foo_arr[2] ='cc';
$foo_arr[3] ='';
$foo_arr[4] ='';
$foo_arr[5] ='dd'
?>

my_array_unique will return:

<?php
$foo_arr[0] ='aa';
$foo_arr[1] ='bb';
$foo_arr[2] ='cc';
$foo_arr[3] ='dd'
?>

martin at lucas-smith dot co dot uk (27-Jan-2003 01:12)

To get a list of the duplicated values in an array, array_unique isn't much help. Instead, use array_filter in conjunction with a callback function, as below:

<?php
$checkKeysUniqueComparison = create_function('$value','if ($value > 1) return true;');
$result = array_keys (array_filter (array_count_values($array), $checkKeysUniqueComparison));
?>

These two lines therefore will create $result, an array of duplicated values in the array $array, once each. E.g. the array
$array = array ("a", "b", "a", "b", "x", "y", "z", "x");
gives the result
Array([0] => a [1] => b [2] => x)

deigo at swirve dot NOSPAM dot com (23-Sep-2002 06:04)

Before I found the mysql distinct I had to make a nicer array from the keys/values that I got from array_unique so.

<?php
$groups=array_unique($groups);
$newgroup[0]=reset($groups);
for ($x=1;$x<sizeof($groups);$x++)
{
  $newgroup[$x]=next($groups);
}
?>

php at hp-site dot dk (29-Aug-2002 07:15)

Try this:
array_flip(array_flip($array));

It gives the same result as the old array_unique()

(29-Aug-2002 10:39)

<?php
$truc = array("l810u00","l810u00","l810q00");
$machin = array_unique($truc);
for($i=0;$i < count($machin) ; $i++){
print $machin[$i]."
";
}
?>
result :
l810u00

This is not strange: $machin (as returned by array unique), contains "l810u00" either in key[0] or key[1] but not both (the key depends on the ersion of PHP), and "l810q00" in key[2].
The returned array has TWO elements so count($machin)==2.
The returned array has a hole in it, and you're not displaying its full content. You could verify it by using this display loop instead:
foreach($machine as $key=>$value){
print '[' . $key . '] => ' . $value . '
";
}
result:
[0] => l810q00
[2] => l810u00
(the first line may display [1] instead of [0] for PHP 4.0.1p3, but you'll get the same order of values and two lines, as expected). When calling array_values() on the result, you're building a new array with the same values in the same order, but with renumbered keys (without holes in numeric keys).

spunk at dasspunk dot NOSPAM dot com (14-Nov-2001 12:52)

I needed a way of retaining the original array's keys in the new, unique array. I came up with this. It works for my purposes but may need refinement.

<?php
function my_array_unique($somearray)
{
    asort($somearray);
    reset($somearray);
    $currentarrayvar = current($somearray);
    foreach ($somearray as $key=>$var)
    {
        if (next($somearray) != $currentarrayvar)
        {
            $uniquearray[$key] = $currentarrayvar;
            $currentarrayvar = current($somearray);
        }
    }
    reset($uniquearray);
    return $uniquearray;
}
?>

az at top-webdesign dot de (10-Jul-2001 09:00)

Attention!
If you use array_unique be aware of data-types! (I spent hours of debugging because of that ...).

For example, if you've got an array containing a '3' as number and another '3' as string it won't be eliminated by array_unique.

An Example where this can happen, without really thinking about it:

I've got an article-list with product-numbers where the third and fourth digit is the code for the producer. So I read in the file an process it line by line and put each producer-code into an array:
------------------------------
<?php
$i=0;
while($line = fgets($csv, 10000) {
// splitting the line, product_no is the first part:

$data = explode(";", $line);

// putting the producer_code into an array:

$producer_id[$i] = trim(substr($data[0], 2, 2));

// make a special exception:

if(trim(substr($data[0], 2, 2)) == 40) {
$producer_id[$j] = '30';
}

// in the above line if you leave the 30 without the ''
// array_unique won't work!

$i++;
}

$producer_ids = array_values(array_unique($producer_id));
?>
-------------------------------
Result is to have all producer-ID's in an array without dupes.

rein at velt dot net (21-Apr-2001 08:44)

Following code copies unique values from MyArray to TempArray.
Then copies non-empty elements from TempArray to UniqueArray.

Not the most elegant solution, but it works.

<?php
$TempArray = array_unique($MyArray);
while (list($index,$data)=each($TempArray)) {
      if (isempty($data)) {
          $UniqueArray[$index]=$data;
      }
}
?>

jllamas at bal dot com dot mx (26-Sep-2000 05:25)

It seems that array_unique creates an exact copy of the original array and then elimitates duplicate values. It does NOT change the "internal references" of the array. For example:

<?php
    $test_alfa = array();
    $test_alfa[0] = "aa";
    $test_alfa[1] = "aa";
    $test_alfa[2] = "aa";
    $test_alfa[3] = "bb";
    $test_alfa[4] = "aa";
    $test_alfa[5] = "bb";
    $test_alfa[6] = "cc";
    $test_alfa[7] = "bb";
  
    $test_beta= array_unique($test_alfa);
    $numValues = count($test_beta);
    for ($i = 0 ; $i <= 7 ; $i++)
       echo("test_beta[$i] = $test_beta[$i] <br>");
    echo ("Number of elements in test_beta = $numValues ");
?>
will give you the following output:

test_beta[0] =
test_beta[1] = aa
test_beta[2] =
test_beta[3] =
test_beta[4] =
test_beta[5] = bb
test_beta[6] = cc
test_beta[7] =
Number of elements in test_beta = 3

The point is that you won't get the output you'd expect if you think that the values of the non duplicate elements are located in the first three array locations.

<?php
    $numValues = count($test_beta);
    for ($i=0;$i<=$numValues; $i++)
       echo("test_beta[$i] = $test_beta[$i] <br>");
    echo ("Number of elements in test_beta = $numValues ");
?>

will give you:

test_beta[0] =
test_beta[1] = aa
test_beta[2] =
Number of elements in test_beta = 3

Hope that saves u some debugging time!