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is_array

(PHP 4, PHP 5)

is_array — 检测变量是否是数组

描述

bool is_array ( mixed $var )

如果 var 是 array，则返回 TRUE，否则返回 FALSE。

参见 is_float()、is_int()、is_integer()、is_string() 和 is_object()。

Variable handling 函数
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PHP手册 - N: 检测变量是否是数组

用户评论:

magentix at gmail dot com (26-Feb-2011 05:12)

If you wanted to have 'pure' associative arrays,
you could filter out non-string keys and then compare the count of the original array with the count of the filtered array.

<?php
    // Only validates empty or completely associative arrays
    function is_assoc ($arr) {
        return (is_array($arr) && count(array_filter(array_keys($arr),'is_string')) == count($arr));
    }

    $a = '';
    $b = 'z';
    $c = array();
    $d = array('x','y','z');
    $e = array('x','y','zed'=>'z');
    $f = array('ex'=>'x','why'=>'y','zed'=>'z');

    echo '$a: ' . ( (is_assoc($a)) ? 'true' : 'false' ) ."\n"; // False
    echo '$b: ' . ( (is_assoc($b)) ? 'true' : 'false' ) ."\n"; // False
    echo '$c: ' . ( (is_assoc($c)) ? 'true' : 'false' ) ."\n"; // True
    echo '$d: ' . ( (is_assoc($d)) ? 'true' : 'false' ) ."\n"; // False
    echo '$e: ' . ( (is_assoc($e)) ? 'true' : 'false' ) ."\n"; // False
    echo '$f: ' . ( (is_assoc($f)) ? 'true' : 'false' ) ."\n"; // True
?>   

I've tested the point of checking whether the array is empty first.
The overall result was a 200% speed increase when the array was indeed empty,
but an average 10% slow when it had elements inside.

<?php
    /***********************************************************
     *    Benchmarks: checking for empty array vs. not checking  *
     ***********************************************************/
   
    // With empty check
    function is_assoc ($arr) {
        return (is_array($arr) && (!count($arr) || count(array_filter(array_keys($arr),'is_string')) == count($arr)));
    }
   
    function test_speed($arr) {   
        $t = microtime(true);
        for($i = 0; $i < 100000; ++$i) is_assoc($arr);
        return (microtime(true) - $t);
    }
   
    echo '$a: ' . test_speed($a) ."\n"; // 0.20597505569458
    echo '$b: ' . test_speed($b) ."\n"; // 0.19199514389038
    echo '$c: ' . test_speed($c) ."\n"; // 0.28803396224976
    echo '$d: ' . test_speed($d) ."\n"; // 0.94685983657837
    echo '$e: ' . test_speed($e) ."\n"; // 0.96698403358459
    echo '$f: ' . test_speed($f) ."\n"; // 0.98052096366882
   
    // Without empty check
    function is_assoc_2 ($arr) {
        return (is_array($arr) && count(array_filter(array_keys($arr),'is_string')) == count($arr));
    }
   
    function test_speed_2($arr) {   
        $t = microtime(true);
        for($i = 0; $i < 100000; ++$i) is_assoc_2($arr);
        return (microtime(true) - $t);
    }
   
    echo '$a: ' . test_speed_2($a) ."\n"; // 0.18811202049255 = FASTER:  91.3% of is_assoc
    echo '$b: ' . test_speed_2($b) ."\n"; // 0.18782901763916 = FASTER:  97.8% of is_assoc
    echo '$c: ' . test_speed_2($c) ."\n"; // 0.64437484741211 = SLOWER: 223.7% of is_assoc
    echo '$d: ' . test_speed_2($d) ."\n"; // 0.84632205963135 = FASTER:  89.4% of is_assoc
    echo '$e: ' . test_speed_2($e) ."\n"; // 0.86739897727966 = FASTER:  89.7% of is_assoc
    echo '$f: ' . test_speed_2($f) ."\n"; // 0.87963700294495 = FASTER:  89.7% of is_assoc
?>

JTS (08-Jun-2010 12:22)

I would change the order of the comparison, because if it is really an empty array, it is better to stop at that point before doing several 'cpu & memory intensive' function calls.

In the end on a ratio of 3 not empty arrays to 1 empty array computed for 1000000 iterations it needed 10% less time.
Or the other way round:
It needed approx 3% to 4% more time if the array is not empty, but was at least 4 times faster on empty arrays.

Additionally the memory consumption veritably lesser.

<?php
function is_assoc($array) {
    return (is_array($array) && (count($array)==0 || 0 !== count(array_diff_key($array, array_keys(array_keys($array))) )));
}
?>

hperrin at gmail dot com (28-May-2010 06:02)

I've found a faster way of determining an array. If you use is_array() millions of times, you will notice a *huge* difference. On my machine, this method takes about 1/4 the time of using is_array().

Cast the value to an array, then check (using ===) if it is identical to the original.

<?php
if ( (array) $unknown !== $unknown ) {
    echo '$unknown is not an array';
} else {
    echo '$unknown is an array';
}
?>

You can use this script to test the speed of both methods.

<pre>
What's faster for determining arrays?

<?php

$count = 1000000;

$test = array('im', 'an', 'array');
$test2 = 'im not an array';
$test3 = (object) array('im' => 'not', 'going' => 'to be', 'an' => 'array');
$test4 = 42;
// Set this now so the first for loop doesn't do the extra work.
$i = $start_time = $end_time = 0;

$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
    if (!is_array($test) || is_array($test2) || is_array($test3) || is_array($test4)) {
        echo 'error';
        break;
    }
}
$end_time = microtime(true);
echo 'is_array  :  '.($end_time - $start_time)."\n";

$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
    if (!(array) $test === $test || (array) $test2 === $test2 || (array) $test3 === $test3 || (array) $test4 === $test4) {
        echo 'error';
        break;
    }
}
$end_time = microtime(true);
echo 'cast, === :  '.($end_time - $start_time)."\n";

echo "\nTested $count iterations."

?>
</pre>

Prints something like:

What's faster for determining arrays?

is_array  :  7.9920151233673
cast, === :  1.8978719711304

Tested 1000000 iterations.

Anonymous (16-May-2009 10:18)

Using empty() in the previous example posted by Anonymous will result in a "Fatal error: Can't use function return value in write context".  I suggest using count() instead:

<?php
function is_assoc($array) {
    return (is_array($array) && 0 !== count(array_diff_key($array, array_keys(array_keys($array)))));
}
?>

Anonymous (06-May-2009 12:34)

strictly speaking: array_diff_key does not return boolean, so using it in a comparison might eventually be considered 'bad'.
perhaps add a bit more cruft...?

<?php
function is_assoc($var)
{
        return is_array($var) AND ! empty ( array_diff_key($var,array_keys(array_keys($var))));
}
?>

skaimauve at yahoo dot ca (03-Mar-2009 08:12)

Or you could make use of the array_diff_key and array_key function:

<?php

function is_assoc($var)
{
        return is_array($var) && array_diff_key($var,array_keys(array_keys($var)));
}

function test($var)
{
        echo is_assoc($var) ? "I'm an assoc array.\n" : "I'm not an assoc array.\n";
}

// an assoc array
$a = array("a"=>"aaa","b"=>1,"c"=>true);
test($a);

// an array
$b = array_values($a);
test($b);

// an object
$c = (object)$a;
test($c);

// other types
test($a->a);
test($a->b);
test($a->c);

?>

The above code outputs:
I'm an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.

Matthias Loitsch (03-Dec-2008 07:36)

Or you could make use of the array_diff_key and range functions:

<?php

function isVector($var) { return count(array_diff_key($var, range(0, count($var) - 1))) == 0; }

function isAssociative($var) { return !isVector($var); }

?>

jim at akubo dot net (28-Oct-2008 07:02)

yousef's example was wrong because is_vector returned true instead of false if the key was found
here is the fixed version (only 2 lines differ)
<?php
function is_vector( &$array ) {
   if ( !is_array($array) || empty($array) ) {
      return -1;
   }
   $next = 0;
   foreach ( $array as $k => $v ) {
      if ( $k !== $next ) return false;
      $next++;
   }
   return true;
}
?>

yousuf at philipz dot com (16-Oct-2008 11:41)

alex frase's example is fast but elanthis at awesomeplay dot com's example is faster and Ilgar's modification of alex's code is faulty (the part " || $_array[$k] !== $v"). Also, Ilgar's suggestion of giving a false return value when the variable isnt an array is not suitable in my opinion and i think checking if the array is empty would also be a suitable check before the rest of the code runs.

So here's the modified (is_vector) version

<?php
function is_vector( &$array ) {
   if ( !is_array($array) || empty($array) ) {
      return -1;
   }
   $next = 0;
   foreach ( $array as $k => $v ) {
      if ( $k !== $next ) return true;
      $next++;
   }
   return false;
}
?>

and the modified (alex's is_assoc) version

<?php
function is_assoc($_array) {
    if ( !is_array($_array) || empty($array) ) {
        return -1;
    }
    foreach (array_keys($_array) as $k => $v) {
        if ($k !== $v) {
            return true;
        }
    }
    return false;
}
?>

alex frase (16-Jul-2008 04:05)

Yet another simpler, faster is_assoc():

<?php
function is_assoc($array) {
  foreach (array_keys($array) as $k => $v) {
    if ($k !== $v)
      return true;
  }
  return false;
}
?>

In my tests it runs about twice as fast as Michael/Gabriel's array_reduce() method.

(Speaking of which: Gabriel's version doesn't work as written; it reports associative arrays as numeric if only the first key is non-numeric, or if the keys are numeric but ordered backwards.  Michael solves this problem by comparing array_reduce() to count(), but that costs another function call; it also works to just compare to -1 instead of 0, and therefore return -1 as the ternary else from the callback).

Michael (11-Sep-2007 08:37)

A slight modification of what's below:

<?php

function is_assoc($array)
{
    return is_array($array) && count($array) !== array_reduce(array_keys($array), 'is_assoc_callback', 0);
}

function is_assoc_callback($a, $b)
{
    return $a === $b ? $a + 1 : 0;
}

?>

gabriel at bumpt dot nothing-here dot net (29-Aug-2007 04:34)

Yet another safer, faster way of detecting whether an array is associative.

The principle is: using array reduction on the keys, we verify that each key is numeric and is equal to its rank.

Beware: integer keys that are not in sequence, or are negative, or with "holes", still make an associative array.

<?php
/**
  * @param array $arr
  * @returns boolean
  */
function isNotAssocArray($arr)
{
    return (0 !== array_reduce(
        array_keys($arr),
        create_function('$a, $b', 'return ($b === $a ? $a + 1 : 0);'),
        0
        )
    );
}
?>

Of course, it is still faster if the callback for array_reduce is not an anonymous function:

<?php
function callbackReduceNotArray($a, $b)
{
    return ($b === $a ? $a + 1 : 0);
}
function isVector($arr)
{
    return (0 !== array_reduce(
        array_keys($arr),
        'callbackReduceNotArray',
        0
        )
    );
}
?>

Alfred J Fazio <alfred dot fazio at gmail dot com> (05-Apr-2007 12:32)

Yet another associative array test:

<?php
function binary_nand ($a, $b) { return !$a && !$b; }
function binary_nor ($a, $b)  { return !$a || !$b; }

// Returns true if array has elements with non-numeric keys
function is_associative_array ($arr) {
  return is_array($arr) && !empty($arr) && array_reduce(array_map("is_numeric", array_keys($arr)), "binary_nor", true);
}

// Returns true if all elements of array have a non-numeric key
function is_strict_associative_array ($arr) {
  return is_array($arr) && !empty($arr) && array_reduce(array_map("is_numeric", array_keys($arr)), "binary_nand", false);
}
?>

angelo [at] mandato <dot> com (26-Feb-2007 09:32)

The is_associative_array() and is_sequential_array() functions posted by 'rjg4013 at rit dot edu' are not accurate.

The functions fail to recognize indexes that are not in sequence or in order.  For example, array(0=>'a', 2=>'b', 1=>'c') and array(0=>'a', 3=>'b', 5=>'c') would be considered as sequential arrays. A true sequential array would be in consecutive order with no gaps in the indices.

The following solution utilizes the array_merge properties. If only one array is given and the array is numerically indexed, the keys get re-indexed in a continuous way.  The result must match the array passed to it in order to truly be a numerically indexed (sequential) array.  Otherwise it can be assumed to be an associative array (something unobtainable in languages such as C).

The following functions will work for PHP >= 4.

<?php
    function is_sequential_array($var)
    {
        return (array_merge($var) === $var && is_numeric( implode( array_keys( $var ) ) ) );
    }
   
    function is_assoc_array($var)
    {
        return (array_merge($var) !== $var || !is_numeric( implode( array_keys( $var ) ) ) );
    }
?>

If you are not concerned about the actual order of the indices, you can change the comparison to == and != respectively.

jupiter at nospam dot com (30-May-2006 07:42)

Will check a Multi-Dimentional Array to any specified level.  This is a fix to 11/16/05 submission, which would break since you must supply a foreach with an array. Beware recursive functions shouldn't go over 100 deep or could break the memory stack on server.

<?php
// checks for multiarray to defined depth level recursively
// original $level must be 2 or more, else will instantly return true
function isDeepMultiArray($multiarray, $level = 2) {  // default is simple multiarray
    if (is_array($multiarray)) {  // confirms array
        if ($level == 1) {  // $level reaches 1 after specified # of recursions 
            return true;  // returns true to recursive function conditional
        }  // end conditional
        foreach ($multiarray as $array) {  // goes one level deeper into array
            if (isDeepMultiArray($array, $level - 1)) {  // check subarray
                $message = "I'm a multiarray";  // optional message
                return $message;  // best if $message = true so function returns boolean
            }  // end recursive function
        }  // end loop
    } else {  // not an array at specified level
    return false;  // is also used recursively so can't change to message
    }
}

if (isDeepMultiArray(array(array()), 2)); // beware this returns true eventhough arrays are empty

?>
BTW my notation is consistent with the PEAR manual on coding standards, which is what php.net says to follow. I hope a function like this gets included in PHP6.

jupiter at nospam dot com (30-May-2006 05:15)

Simple check for a Multi-Dimentional Array of any depth
<?php
// checks for multiarray (2 or more levels deep)
function isMultiArray($multiarray) {
  if (is_array($multiarray)) {  // confirms array
    foreach ($multiarray as $array) {  // goes one level deeper
      if (is_array($array)) {  // is subarray an array
        return true;  // return will stop function
      }  // end 2nd check
    }  // end loop
  }  // end 1st check
  return false;  // not a multiarray if this far
}
?>

March (30-Mar-2006 02:28)

And here is another variation for a function to test if an array is associative. Based on the idea by mot4h.

<?php
function is_associative($array)
{
  if (!is_array($array) || empty($array))
    return false;

  $keys = array_keys($array);
  return array_keys($keys) !== $keys;
}
?>

dan at cain dot sh (11-Dec-2004 01:05)

is_array() under PHP 5.0.2 will return FALSE when passed an object descended from the internal class interface ArrayAccess(http://www.php.net/spl) even though said object behaves as an array would in most instances.

I've found the following user function helpful with my own classes and functions that expect array(s) as arguments, but work fine with objects that behave as an array would.

<?php
function is_array_abled(&$x)
{
    return (bool)($x instanceof ArrayAccess or is_array($x));
}
?>

vhermecz at ixpert dot hu (02-Apr-2004 12:58)

Mike's function is quite cool, it is just the one, I was searching for. Using range is a great idea! But it's a bit long for me. Here is a shorter version:

<?php
function is_assoc_array($var) {
    if (!is_array($var)) {
        return false;
    }
    return array_keys($var)!==range(0,sizeof($var)-1);
}
?>

Or, if you don't want to type that much:

<?php
function is_assoc($var) {
    return is_array($var) && array_keys($var)!==range(0,sizeof($var)-1);
}
?>

mike-php at spam dot emerge2 dot spam dot com (22-Aug-2003 11:20)

All arrays in PHP are associative arrays, but it is quite easy to treat an associative array just like it is a sequential array. However, when dealing with XML-RPC, it is necessary to know whether an array is associative or sequential, so I created this function.

It isn't perfect, since an associative array that just happens to have sequential, integer keys starting with 0 will 'look' exactly like a sequential array, and will fool this function.

<?php
/****************************************************************
* is_assoc_array tries to decide whether or not a given array   *
* is an associative array, or a sequential array. Of course, no *
* such distinction is made by PHP, so it really just tests      *
* whether or not a given array could possibly be a sequential   *
* array. Since an associative array with sequential, integer    *
* keys 'looks' just like a sequential array, this function will *
* be fooled.                                                    *
*                                                               *
* BUG: Associative arrays with sequential, integer keys 'look'  *
* just like sequential arrays, and will be identified as such.  *
*                                                               *
****************************************************************/
function is_assoc_array( $php_val ) {
   if( !is_array( $php_val ) ){
      # Neither an associative, nor non-associative array.
      return false;
   }

   $given_keys = array_keys( $php_val );
   $non_assoc_keys = range( 0, count( $php_val ) );

   if( function_exists( 'array_diff_assoc' ) ) { # PHP > 4.3.0
      if( array_diff_assoc( $given_keys, $non_assoc_keys ) ){
         return true;
      }
      else {
         return false;
      }
   }
   else {
      if( array_diff( $given_keys, $non_assoc_keys ) and array_diff( $non_assoc_keys, $given_keys ) ){
         return true;
      }
      else {
         return false;
      }
   }
}
?>