数组 函数
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array_diff_assoc

(PHP 4 >= 4.3.0, PHP 5)

array_diff_assoc — 带索引检查计算数组的差集

说明

array array_diff_assoc ( array $array1 , array $array2 [, array $ ... ] )

array_diff_assoc() 返回一个数组，该数组包括了所有在 array1 中但是不在任何其它参数数组中的值。注意和 array_diff() 不同的是键名也用于比较。

Example #1 array_diff_assoc() 例子

<?php
$array1 = array ("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array ("a" => "green", "yellow", "red");
$result = array_diff_assoc($array1, $array2);
?>

以上例程会输出：

Array
(
    [b] => brown
    [c] => blue
    [0] => red
)

上面的例子中可以看到键值对 "a" => "green" 在两个数组中都有，因此不在本函数的输出中。与此不同，键值对 0 => "red" 出现在输出中是因为第二个参数中的 "red" 的键名是 1。

键值对 key => value 中的两个值仅在 (string) $elem1 === (string) $elem2 时被认为相等。也就是说使用了严格检查，字符串的表达必须相同。

Note: 注意本函数只检查了多维数组中的一维。当然可以用 array_diff_assoc($array1[0], $array2[0]); 检查更深的维度。

参见 array_diff()，array_intersect() 和 array_intersect_assoc()。

参数

array1

The array to compare from

array2

An array to compare against

...

More arrays to compare against

返回值

Returns an array containing all the values from array1 that are not present in any of the other arrays.

范例

Example #2 array_diff_assoc() example

In this example you see the "a" => "green" pair is present in both arrays and thus it is not in the output from the function. Unlike this, the pair 0 => "red" is in the output because in the second argument "red" has key which is 1.

<?php
$array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array("a" => "green", "yellow", "red");
$result = array_diff_assoc($array1, $array2);
print_r($result);
?>

以上例程会输出：

Array
(
    [b] => brown
    [c] => blue
    [0] => red
)

Example #3 array_diff_assoc() example

Two values from key => value pairs are considered equal only if (string) $elem1 === (string) $elem2 . In other words a strict check takes place so the string representations must be the same.

<?php
$array1 = array(0, 1, 2);
$array2 = array("00", "01", "2");
$result = array_diff_assoc($array1, $array2);
print_r($result);
?>

以上例程会输出：

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

注释

Note: This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using, for example, array_diff_assoc($array1[0], $array2[0]);.

参见

数组 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 带索引检查计算数组的差集

用户评论:

news_yodpeirs at thoftware dot de (12-Jul-2011 12:25)

A quite simple (yet not very efficient) way to compare the first level of arrays which have values that are not strings:
array_map('unserialize',array_diff_assoc(array_map('serialize',$arr1),array_map('serialize',$arr2)))
Might be useful for debugging (that's what I use it for).

55 dot php at imars dot com (17-Mar-2009 03:09)

I've worked on array_diff_assoc_recursive() mentioned by chinello at gmail dot com and I think it might be worth mentioning here. I wrote a dozen test cases and it seems to be holding up pretty well.

<?php
// dwarven Differences:
// * Replaced isset() with array_key_exists() to account for keys with null contents

// 55 dot php at imars dot com Differences:
// Key differences:
// * Removed redundant test;
// * Returns false bool on exact match (not zero integer);
// * Use type-precise comparison "!==" instead of loose "!=";
// * Detect when $array2 contains extraneous elements;
// * Returns "before" and "after" instead of only "before" arrays on mismatch.

function array_compare($array1, $array2) {
    $diff = false;
    // Left-to-right
    foreach ($array1 as $key => $value) {
        if (!array_key_exists($key,$array2)) {
            $diff[0][$key] = $value;
        } elseif (is_array($value)) {
             if (!is_array($array2[$key])) {
                    $diff[0][$key] = $value;
                    $diff[1][$key] = $array2[$key];
             } else {
                    $new = array_compare($value, $array2[$key]);
                    if ($new !== false) {
                         if (isset($new[0])) $diff[0][$key] = $new[0];
                         if (isset($new[1])) $diff[1][$key] = $new[1];
                    };
             };
        } elseif ($array2[$key] !== $value) {
             $diff[0][$key] = $value;
             $diff[1][$key] = $array2[$key];
        };
 };
 // Right-to-left
 foreach ($array2 as $key => $value) {
        if (!array_key_exists($key,$array1)) {
             $diff[1][$key] = $value;
        };
        // No direct comparsion because matching keys were compared in the
        // left-to-right loop earlier, recursively.
 };
 return $diff;
};
?>

Note that to catch small type differences, you need to use var_dump() rather than print_r(). For example:

<?php
first = Array( 'first' => 'second', 'third' => 'fourth',
  'fifth' => Array( 'oui' => 'yes', 'non' => 'no' ),
  'sixth' => Array( 3, 4, 2, 1 )
);
$second = Array( 'first' => 'second', 'third' => 'fourth',
  'fifth' => Array( 'oui' => 'yes', 'non' => 'no' ),
  'sixth' => Array( 3, 4, '2', 1 )
);
$diff = array_compare($first, $second);
if ($diff === false) echo "MATCH\n";
else var_dump($diff);
?>

The above would immediately show that element "sixth", index 2, is int(2) in $first but string(1)"2" in $second. As per the original function, order for associative arrays does not matter, and of course it does with lists.

[EDIT: Credits to php dot notes at dwarven dot co dot uk]

jrajpu10 at gmail dot com (25-Oct-2008 08:57)

array_diff_assoc can also be used to find the duplicates in an array

<?php
$arr = array('1','2','3','4','3','2','5');
$uniques = array_unique($arr);
// array_diff will not work here, array_diff_assoc works as it takes the key // in account.
$dups = array_diff_assoc($arr, $uniques);

print_r($dups);
?>

Note: The index of the $dups is not in strict sequential order as expected by C programmer.

cedric at daneel dot net (21-May-2007 02:01)

To diff between n-dimensional array, juste use this :

<?php
function array_diff_values($tab1, $tab2)
    {
    $result = array();
    foreach($tab1 as $values) if(! in_array($values, $tab2)) $result[] = $values;
    return $result;
    }
?>

contact at pascalopitz dot com (11-Apr-2007 12:14)

The direction of the arguments does actually make a difference:

<?php
$a = array(
    'x' => 'x',
    'y' => 'y',
    'z' => 'z',
    't' => 't',
);

$b = array(
    'x' => 'x',
    'y' => 'y',
    'z' => 'z',
    't' => 't',
    'g' => 'g',
);

print_r(array_diff_assoc($a, $b));
print_r(array_diff_assoc($b, $a));
?>

echoes:

Array
(
)
Array
(
    [g] => g
)

chinello at gmail dot com (19-Mar-2007 06:33)

The following will recursively do an array_diff_assoc, which will calculate differences on a multi-dimensional level.  This not display any notices if a key don't exist and if error_reporting is set to E_ALL:

<?php
function array_diff_assoc_recursive($array1, $array2)
{
    foreach($array1 as $key => $value)
    {
        if(is_array($value))
        {
              if(!isset($array2[$key]))
              {
                  $difference[$key] = $value;
              }
              elseif(!is_array($array2[$key]))
              {
                  $difference[$key] = $value;
              }
              else
              {
                  $new_diff = array_diff_assoc_recursive($value, $array2[$key]);
                  if($new_diff != FALSE)
                  {
                        $difference[$key] = $new_diff;
                  }
              }
          }
          elseif(!isset($array2[$key]) || $array2[$key] != $value)
          {
              $difference[$key] = $value;
          }
    }
    return !isset($difference) ? 0 : $difference;
}
?>

[NOTE BY danbrown AT php DOT net: This is a combination of efforts from previous notes deleted.  Contributors included (Michael Johnson), (jochem AT iamjochem DAWT com), (sc1n AT yahoo DOT com), and (anders DOT carlsson AT mds DOT mdh DOT se).]

Alexander Podgorny (30-May-2006 10:30)

NOTE: the diff_array also removes all the duplicate values that match to the values in the second array:

<?php
    $array1 = array("a","b","c","a","a");
    $array2 = array("a");

    $diff = array_diff($array1,$array2);

    // yields: array("b","c") the duplicate "a" values are removed
?>

benjamin at moonfactory dot co dot jp (12-Jan-2005 05:56)

Hi all,
For php versions < 4.3...

<?php
/**
 * array_diff_assoc for version < 4.3
 **/
if (!function_exists('array_diff_assoc'))
{
    function array_diff_assoc($a1, $a2)
    {
        foreach($a1 as $key => $value)
        {
            if(isset($a2[$key]))
            {
                if((string) $value !== (string) $a2[$key])
                {
                     $r[$key] = $value;
                }
            }else
            {
                $r[$key] = $value;
            }
        }
        return $r ;
    }
}

?>

carl at thep dot lu dot se (09-May-2003 10:55)

To unset elements in an array if you know the keys but not the values, you can do:

<?php
$a = array("foo", "bar", "baz", "quux");
$b = array(1, 3); // Elements to get rid of

foreach($b as $e)
  unset($a[$e]);
?>

Of course this makes most sense if $b has many elements or is dynamically generated.