is_array

(PHP 4, PHP 5, PHP 7, PHP 8)

is_array — 检测变量是否是数组

描述

is_array ( mixed $var ) : bool

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()。

User Contributed Notes

Daniel 14-Jul-2019 06:54
The next post is not correct because has problems with blank array index:
https://www.php.net/manual/es/function.is-array.php#89332

The next code use the above link php code

<?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);

// maybe assoc array?
$b = array(0 => "aaa", 1 => 1, 3 => true); // Index 2 not exist
test($b);
?>

# Output
I'm an assoc array.
I'm an assoc array.

"Associative arrays are arrays that use named keys that you assign to them."
https://www.w3schools.com/php/php_arrays.asp

Solution:

<?php
function is_assoc(array $array)
{
    return count(array_filter(array_keys($array), 'is_string')) > 0;
}
function test(array $array)
{
    echo is_assoc($array) ? "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
$b = array(0=>"aaa",1=>1,3=>true);
test($b);
?>

# Output
I'm an assoc array.
I'm not an assoc array.

If you want check pure assoc. array replace > 0 by === count($array)
lrgbx0 at gmail dot com 10-May-2018 08:48
is_assoc() Benchmark:

<?php

function is_assoc1($array) {
    if (!is_array($array)) return false;
    $i = count($array);
    while ($i > 0) unset($array[--$i]);
    return (bool)$array;
}

function is_assoc2(&$array) {
    if (!is_array($array)) return false;
    $i = count($array);
    while ($i > 0) {
        if (!isset($array[--$i])) return true;
    }
    return false;
}

function is_assoc3(&$array) {
    if (!is_array($array)) return false;
    $i = count($array);
    while ($i > 0) {
        if (!array_key_exists(--$i, $array)) return true;
    }
    return false;
}

function is_assoc4($array) {
    if (!is_array($array)) return false;
    ksort($array);
    foreach (array_keys($array) as $k => $v) {
        if ($k !== $v) return true;
    }
    return false;
}

function is_assoc5(&$array) {
    return is_array($array) && array_diff_key($array, array_keys($array));
}

$arr1 = array(); // not associative
$arr2 = $arr3 = array('foo', 'bar', 'baz', 'foo', 'bar', 'baz', 'foo', 'bar', 'baz', 'foo'); // not associative
asort($arr3); // not associative, shuffled keys
$arr4 = array('foo', 'bar', 'baz', 'foo', 'bar', null, 'foo', 'bar', 'baz', 'foo'); // not associative but is_assoc2() thinks it is
$arr5 = array(0 => 'foo', 1 => 'bar', 2 => 'baz', 3 => 'foo', 4 => 'bar', 5 => 'baz', 'foo3' => 'foo', 'bar3' => 'bar', 'baz3' => 'baz', 'foo4' => 'foo'); // associative

$i = $j = 0;
$time = array(0.0, 0.0, 0.0, 0.0, 0.0);

for ($j = 0; $j < 2000; $j++) {
    $time[0] -= microtime(true);
    for ($i = 0; $i < 1000; $i++) {
        if (is_assoc1($arr1) || is_assoc1($arr2) || is_assoc1($arr3) || is_assoc1($arr4) || !is_assoc1($arr5)) {
            echo 'error';
            break;
        }
    }
    $time[0] += microtime(true);
    $time[1] -= microtime(true);
    for ($i = 0; $i < 1000; $i++) {
        if (is_assoc2($arr1) || is_assoc2($arr2) || is_assoc2($arr3) || !is_assoc2($arr4) || !is_assoc2($arr5)) { // $arr4 tweaked
            echo 'error';
            break;
        }
    }
    $time[1] += microtime(true);
    $time[2] -= microtime(true);
    for ($i = 0; $i < 1000; $i++) {
        if (is_assoc3($arr1) || is_assoc3($arr2) || is_assoc3($arr3) || is_assoc3($arr4) || !is_assoc3($arr5)) {
            echo 'error';
            break;
        }
    }
    $time[2] += microtime(true);
    $time[3] -= microtime(true);
    for ($i = 0; $i < 1000; $i++) {
        if (is_assoc4($arr1) || is_assoc4($arr2) || is_assoc4($arr3) || is_assoc4($arr4) || !is_assoc4($arr5)) {
            echo 'error';
            break;
        }
    }
    $time[3] += microtime(true);
    $time[4] -= microtime(true);
    for ($i = 0; $i < 1000; $i++) {
        if (is_assoc5($arr1) || is_assoc5($arr2) || is_assoc5($arr3) || is_assoc5($arr4) || !is_assoc5($arr5)) {
            echo 'error';
            break;
        }
    }
    $time[4] += microtime(true);
}

echo 'is_assoc1(): ' . $time[0] . "\n";
echo 'is_assoc2(): ' . $time[1] . "\n";
echo 'is_assoc3(): ' . $time[2] . "\n";
echo 'is_assoc4(): ' . $time[3] . "\n";
echo 'is_assoc5(): ' . $time[4] . "\n";

?>

is_assoc1() - uses unset(), a bit slow, but mem friendly and no function calls
is_assoc2() - uses isset(), fastest one, but returns TRUE whenever array contains NULL
is_assoc3() - fixed is_assoc2(), uses array_key_exists(), fast and memory friendly, and much smarter than the following (no need to check all those keys)
is_assoc4() - alex' version with proper check and key sorting
is_assoc5() - fixed a bit JTS' version, really nice one, but uses too many functions and checks all keys

Results:

is_assoc1(): 2.1628699302673
is_assoc2(): 1.1079933643341
is_assoc3(): 1.7120850086212
is_assoc4(): 3.9194552898407
is_assoc5(): 1.9509885311127
rik at mmod dot co 12-Apr-2018 05:39
Using is_array prior to an in_array within an if clause will safely escape a check against a variable that could potentially be a non-array when using in_array.  For instance:

NOTE: A real use case might be that we have a list of possible flags which  in a database we have stored whether each of the flags are 0 or 1.  We want a list of the flags which have the value of 1 to be returned.

Our example here will not use so many technical artifacts, but will be based on similar logic just to get the point across.

<?php

// We have a list of known values
$knownVars = ['apple', 'orange'];

// A list of values to check
$listToCheck = ['pear', 'banana'];

// And a method that takes a list of values to check and returns a new list
// of the items from said list that are found to be valid...
public function getValidItemsList( $listToCheck /*['pear', 'banana']*/)
{
    $returnList = [];
    foreach($listToCheck as $key => $val)
    {
        if(in_array($val, $knownVars))
        {
            array_push($returnList, $val);
        }
    }

    if(empty($returnList))
    {
        // We have a special case if there were no valid items found, which is the case we are going over
        return  -1;
    }

    // Otherwise, normally returns a list of the items that were found to be valid
    return $returnList;
}

// Call the method and check for any valid items that can be used for some purpose
$validItemsList =  getValidItemsList($listToCheck);

// In this usage we could potentially get an exception because
// in_array() expects an array for argument #2, checking that the value != -1 does not escape the if statement:
if(isset($validItemsList) && $validItemsList != -1 && in_array('apple', $validItemsList))
{
    //...
}

// In this usage, we break free from the if statement safely:
if(isset($validItemsList) && $validItemsList != -1 && is_array($validItemsList) && in_array('apple', $validItemsList))
{
    //...
}

?>

Hope that can help someone, I know it helped me.
gwschnell at ewe dot net 22-Mar-2018 04:58
An error will be thrown If is_array() is applied to a nonexisting varble.
carren at AngieBecker dot ch 26-Sep-2017 08:48
This is probably the best way to test for associative arrays:

<?php
function is_assoc($test) {
        if (empty($test)) { return(false); }
        if (!is_array($test)) { return(false); }
        return ($test !== array_values($test));
}
?>

This version is based on the one from dmitry dot sushilov, which is unfortunately exactly opposite and misses the is_array and empty test.
http://php.net/manual/en/function.is-array.php#115901
marko at newvibrations dot net 20-Oct-2016 12:08
hperrin at gmail dot com
i tested modified version of your code:

<?php
$test = array_fill(0, $size, rand());
$test3 = (object) $test;   
?>

Results are quite different!

PHP 5.5:
is_array - execution time is constant over different $size
cast, === - execution time is proportional with $size, for small arrays, it's faster than is_array, but for bigger arrays, it's way slower. Also, bigger memory allocation because casting actually allocates memory

PHP 7.0:
is_array and cast, === have constant execution time over different $size:
is_array  :  0.12564396858215
cast, === :  0.24629783630371

Looks like casting is optimised, but still slower.

Bottom line is: optimisation is not done for special scenario, but for average use and scalability. Don't reinvent wheel.
Rob Thomas 05-Oct-2016 10:40
Please note that the 'cast to array' check is horrendously out of date.

Running that code against PHP 5.6 results in this:

is_array  :  0.93975400924683
cast, === :  1.2425191402435

So, please use 'is_array', not the horrible casting hack.
mt at banita dot de 08-Sep-2016 09:30
I'm using PHP 5.3.10 and the remark from hperrin is not (no longer?) valid

is_array is (now?) faster than if ( (array) $unknown !== $unknown ) 

my result of hperrins test script

is_array  :  0.61710119247437
cast, === :  1.1551909446716
ari at umbrella dot bz 05-Sep-2016 08:34
hperrin's results have indeed changed in PHP 7. The opposite is now true, is_array is faster than comparison:

is_array  :  0.52148389816284
cast, === :  0.84179711341858

Tested 1000000 iterations.
mbrodala at pagemachine dot de 24-Aug-2016 01:22
Notice that the benchmark results from hperrin at gmail dot com have changed in the meantime:

is_array  :  0.31888604164124
cast, === :  0.58448791503906

(Using PHP 5.6.24, I expect other results with PHP 7)
dmitry dot sushilov at gmail dot com 12-Oct-2014 12:49
function is_associate_array($array)
{
    return $array === array_values($array);
}

or you can add check is_array in functions
joksnet at gmail dot com 08-Oct-2013 10:17
Here is something for compare `is_assoc` functions.

<?php
function is_assoc1($var)
{
    return is_array($var) && array_diff_key($var, array_keys(array_keys($var)));
}

function is_assoc2($var)
{
    return is_array($var) && array_diff_key($var, array_fill(0, count($var), null));
}

$count = 1000000;

$a = array('a' => 'foo', 'b' => 1, 'c' => true);
$b = array('a', 'b', 'c');

$i = $start_time = $end_time = 0;

$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
    assert(is_assoc1($a) === true);
    assert(is_assoc1($b) === false);
}
$end_time = microtime(true);
echo 'is_assoc1  :  ' . ($end_time - $start_time) . "\n";

$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
    assert(is_assoc2($a) === true);
    assert(is_assoc2($b) === false);
}
$end_time = microtime(true);
echo 'is_assoc2  :  ' . ($end_time - $start_time) . "\n";
?>

It prints something like this:

```
% php is_assoc.php
is_assoc1  :  19.36315202713
is_assoc2  :  18.954080104828
```

The first one is from
skaimauve (http://www.php.net/manual/en/function.is-array.php#89332). The second one is mine.
magentix at gmail dot com 26-Feb-2011 09:12
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 04:22
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 10:02
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 02:18
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)))));
}
?>
skaimauve at yahoo dot ca 03-Mar-2009 12:12
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 11:36
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 11:02
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 03:41
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 08:05
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 12:37
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 08:34
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> 04-Apr-2007 04:32
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 01:32
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 29-May-2006 11:42
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 29-May-2006 09:15
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 06:28
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 10-Dec-2004 05:05
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 01-Apr-2004 04:58
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);
}
?>