User Contributed Notes

t-fav 19-Oct-2017 10:20
Noted some interesting behaviour when using array_search to find the correct index in an array containing an index with a value of 0.

The following works as expected.

<?php

$dataSet = [];
$dataSet[] = ['name' => 'Row A', 'items' => ['ItemA' => 1, 'ItemB' => 2]];
$dataSet[] = ['name' => 'Row B', 'items' => ['ItemA' => 1, 'ItemB' => 2]];

$rows = [];
foreach ($dataSet as $dataRow) {
    $row = [
        $dataRow['name'],
        'ItemA',
        'ItemB'
    ];
   
    foreach ($dataRow['items'] as $key => $value) {
        $index = array_search($key, $row);
        $row[$index] = $value;
    }
   
    $rows[] = $row;
}

print_r($rows);

It returns:

Array
(
    [0] => Array
        (
            [0] => Row A
            [1] => 1
            [2] => 2
        )
    [1] => Array
        (
            [0] => Row B
            [1] => 1
            [2] => 2
        )
)

However, the following seems to totally ignore the index containing the value 0 and thus returns the wrong index.

<?php

$dataSet = [];
$dataSet[] = ['name' => 'Row A', 'items' => ['ItemA' => 1, 'ItemB' => 2]];
$dataSet[] = ['name' => 'Row B', 'items' => ['ItemA' => 0, 'ItemB' => 2]];

$rows = [];
foreach ($dataSet as $dataRow) {
    $row = [
        $dataRow['name'],
        'ItemA',
        'ItemB'
    ];
   
    foreach ($dataRow['items'] as $key => $value) {
        $index = array_search($key, $row);
        $row[$index] = $value;
    }
   
    $rows[] = $row;
}

print_r($rows);

It returns:

Array
(
    [0] => Array
        (
            [0] => Row A
            [1] => 1
            [2] => 2
        )
    [1] => Array
        (
            [0] => Row B
            [1] => 2
            [2] => ItemB
        )
)

However, setting ItemA's value on Row B to '' or false works fine. Also, passing in the third optional parameter [, bool $strict = true ] works correctly as well. Is this intentional behaviour?
justeme at sina dot com 26-Jul-2017 05:42
/*
Be careful!!!
when i in php7.1.5
below program return int 0
is it a bug?
*/
array_search(0,['a','b','c'])
mohamedn085 at gmail dot com 20-Jun-2017 01:59
Mohamed Nabil

hallo every body This function matches two arrays like
search an array like another or not  array_match which can match

function array_match($arr1,$arr2,$highlevel=false)
{

   $keys1=array_keys($arr1);
   $keys2=array_keys($arr2);

   $values1=array_values($arr1);
   $values2=array_values($arr2);
   
     if ($highlevel)
     {
    
     if ($keys1 === $keys2 && $values1 === $values2)
     {
        
         return true;

     }
       return false;
     }

     if ($keys1 == $keys2 && $values1 == $values2)
     {
        
         return true;

     }
       return false;
   
}
 var_dump(array_match(['id'=>'1','username'=>'2'],['id'=>'1','username'=>2]));
  //Output:true

 var_dump(array_match(['id'=>'1','username'=>'2'],['id'=>'1','username'=>2],true));
 //Output:false
tammander at gmail dot com 07-Apr-2017 01:45
/**
 * Search into multidimensional array all ocurrences of $needle
 *
 * @param String   $needle  value to find
 * @param Array    $arr     multidimensional array where find
 *
 * @return Array            empty array or array of parent keys where found
 *
 */
function search_value_in($needle, $arr)
{
    $result = [];
    $found = 0;
    if (is_array($arr)) {
        foreach ($arr as $in) {
            if (is_array($in)) {
               if (array_search($needle, $in) !== false) {
                   $result[] = $found;
               }
            }
            $found++;
        }
    }
    return $result;
}
turabgarip at gmail dot com 11-Mar-2017 12:04
About searcing in multi-dimentional arrays; two notes on "xfoxawy at gmail dot com";

It perfectly searches through multi-dimentional arrays combined with array_column() (min php 5.5.0) but it may not return the values you'd expect.

<?php array_search($needle, array_column($array, 'key')); ?>

Since array_column() will produce a resulting array; it won't preserve your multi-dimentional array's keys. So if you check against your keys, it will fail.

For example;

<?php
$people = array(
  2 => array(
    'name' => 'John',
    'fav_color' => 'green'
  ),
  5=> array(
    'name' => 'Samuel',
    'fav_color' => 'blue'
  )
);

$found_key = array_search('blue', array_column($people, 'fav_color'));
?>

Here, you could expect that the $found_key would be "5" but it's NOT. It will be 1. Since it's the second element of the produced array by the array_column() function.

Secondly, if your array is big, I would recommend you to first assign a new variable so that it wouldn't call array_column() for each element it searches. For a better performance, you could do;

<?php
$colors = array_column($people, 'fav_color');
$found_key = array_search('blue', $colors);
?>
stocki dot r at gmail dot com 11-Oct-2016 05:26
Be careful, PHP will cast float keys to integers:
nl1.php.net/manual/en/language.types.array.php

<?php
$array = array(
    0.9 => 'abc'
);
$key = array_search('abc', $array); // $key = 0;
?>

Use string keys instead:

<?php
$array = array(
    '0.9' => 'abc'
);
$key = array_search('abc', $array); // $key = '0.9';
?>
hyder7nh at gmail dot com 23-Dec-2015 05:34
When using array_search in if statements with array elements that use integers for keys, if the key [0] matches, the statement would always return false.

This is because array_search returns the key of the value that matches with the first argument. If statements check if the return value is true or false(boolean), 0 is boolean for false.

This problem shouldn't occur with key names that are strings.

<?php

//$f would be 0, because key [0] matches the first argument
$f = array_search('photo', array('photo', 'audio'));

//$f statement would fall to else condition because $f is 0 and 0 is false
if($f==true)
{
    echo 'found<br/>';
}
else
{
    echo 'not found<br/>';
}

if(array_search('photo', array('photo')))
{
    echo 'FOUND';
}
else
{
    echo 'NOT FOUND';
}

Use the === operator to get around this problem.
maciej at speccode dot com 18-Aug-2015 02:58
FYI, remember that strict mode is something that might save you hours.

If you're searching for a string and you have a "true" boolean on the way - you will get it as result (first occurrence). Example below:

<?php

$arr = [
    'foo'    => 'bar',
    'abc'    => 'def',
    'bool'   => true,
    'target' => 'xyz'
];

var_dump( array_search( 'xyz', $arr ) ); //bool
var_dump( array_search( 'xyz', $arr, true ) ); //target

?>
superbueno at gmail dot com 01-May-2015 08:19
Like many others, === failed for a 0-indexed occurrence.  My solution was to test if an integer returned:

if ( is_int ( array_search($value, $array) ) ) return true;
xfoxawy at gmail dot com 02-Feb-2015 08:30
in (PHP 5 >= 5.5.0) you don't have to write your own function to search through a multi dimensional array

ex :

$userdb=Array
(
    (0) => Array
        (
            (uid) => '100',
            (name) => 'Sandra Shush',
            (url) => 'urlof100'
        ),

    (1) => Array
        (
            (uid) => '5465',
            (name) => 'Stefanie Mcmohn',
            (pic_square) => 'urlof100'
        ),

    (2) => Array
        (
            (uid) => '40489',
            (name) => 'Michael',
            (pic_square) => 'urlof40489'
        )
);

simply u can use this

$key = array_search(40489, array_column($userdb, 'uid'));
nan at designpromote dot co dot uk 17-Jan-2015 01:45
$array = ['a', 'b', 'c'];
$key = array_search('a', $array); //$key = 0
if ($key)
{
//even a element is found in array, but if (0) means false
//...
}

//the correct way
if (false !== $key)
{
//....
}

It's what the document stated "may also return a non-Boolean value which evaluates to FALSE."
podarokua at gmail dot com 17-Oct-2014 01:45
Here is a method for getting all keys, containing searched value, recursively

  /**
   * Recursive array search.
   *
   * See http://php.net/manual/en/function.array-search.php#91365
   *
   * @param $needle
   *   The searched value.
   * @param $haystack
   *   The array.
   *
   * @return bool|int|string
   *   Array of keys, containing values or FALSE if not found.
   */
  private function ras($needle, $haystack) {
    $keys = array();
    foreach ($haystack as $key => $value) {
      if ($needle === $value OR (is_array($value) && $this->ras(
            $needle,
            $value
          ) !== FALSE)
      ) {
        $keys[] = $key;
      }
    }
    if (!empty($keys)) {
      return $keys;
    }

    return FALSE;
  }
marvin dot petker at borntocreate dot de 06-Sep-2014 01:08
Be aware of using array_search() in conditional statements.

$foo = array("one", "two");
if( $key = array_search("one", $foo) ){
  echo "Found";
}
else{
  echo "Not found";
}
//Ouput: Not found

"Not found" will be outputted beacause the returned key is 0 and that will be interpreted as false in conditional statements.
dk at danilok dot com 22-Aug-2014 03:26
I needed a way to return the value of a single specific key, thus:

<?php

function recursive_return_array_value_by_key($needle, $haystack){
    $return = false;
    foreach($haystack as $key => $val){
        if(is_array($val)){
            $return = recursive_return_array_value_by_key($needle, $val);
        }
        else if($needle === $key){
            return "$val\n";
        }
    }
    return $return;
}

?>
rAthur 02-Apr-2014 05:35
If you're not running an older version of PHP (many servers are still on PHP 5.3), you can replace the function by this :

<?php

function s($needle,$array)
{
    foreach($array as $key => $value)
        if ($value==$needle)
        return $key;
    return false;
}

echo s( 'c', array('a', 'b', 'c', 'd') ); // returns 2
echo s( 'f', array('a', 'b', 'c', 'd') ); // returns false

?>
sunelbe at gmail dot com 21-Sep-2012 09:19
hey i have a easy multidimensional array search function

<?php
function search($array, $key, $value)
{
    $results = array();

    if (is_array($array))
    {
        if (isset($array[$key]) && $array[$key] == $value)
            $results[] = $array;

        foreach ($array as $subarray)
            $results = array_merge($results, search($subarray, $key, $value));
    }

    return $results;
}
?>
sneskid at hotmail dot com 16-Mar-2012 05:50
I had an array of arrays and needed to find the key of an element by comparing actual reference.
Beware that even with strict equality (===) php will equate arrays via their elements recursively, not by a simple internal pointer check as with class objects. The === can be slow for massive arrays and also crash if they contain circular references.

This function performs reference sniffing in order to return the key for an element that is exactly a reference of needle.

<?php
function array_ref_search(&$v, array &$s)
{
    if(is_object($v)){ return array_search($v, $s, true); }
    foreach($s as $rK => &$rV)
    { // reference sniff
        $tV = $v;
        if( ($rV === ($v = 1)) && ($rV === ($v = 0)) ){
        $v = $tV; return $rK; }
        $v = $tV;
    }
    return false; // use null for php < 4.2.0
}

$list   = array();
$list['A'] = &$valA; $list['B'] = &$valB;

$valA = 1; $valB = 1;
echo 'array_ref_search: ', array_ref_search($valB, $list), '</br>'; // key 'B'
echo 'array_search:     ', array_search($valB, $list, true), '</br>'; // key 'A'

$valA = array(1,2,3); $valB = array(1,2,3);
echo 'array_ref_search: ', array_ref_search($valB, $list), '</br>'; // key 'B'
echo 'array_search:     ', array_search($valB, $list, true), '</br>'; // key 'A' because ($valA === $valB) is true by elements

$valB[] = &$valB; // circular reference
echo 'array_ref_search: ', array_ref_search($valB, $list), '</br>'; // key 'B'
echo 'array_search:     ', array_search($valB, $list, true), '</br>'; // crash because ($valB === $valB) causes infinite loop
?>
revoke 11-Oct-2011 01:12
Better solution of multidimensional searching.

<?php
function multidimensional_search($parents, $searched) {
  if (empty($searched) || empty($parents)) {
    return false;
  }
 
  foreach ($parents as $key => $value) {
    $exists = true;
    foreach ($searched as $skey => $svalue) {
      $exists = ($exists && IsSet($parents[$key][$skey]) && $parents[$key][$skey] == $svalue);
    }
    if($exists){ return $key; }
  }
 
  return false;
}

$parents = array();
$parents[] = array('date'=>1320883200, 'uid'=>3);
$parents[] = array('date'=>1320883200, 'uid'=>5);
$parents[] = array('date'=>1318204800, 'uid'=>5);

echo multidimensional_search($parents, array('date'=>1320883200, 'uid'=>5)); // 1
?>
stooshie at gmail dot com 06-Oct-2011 11:51
Example of a recursive binary search that returns the index rather than boolean.
<?php
// returns the index of needle in haystack
function binSearch($needle, $haystack)
{
    // n is only needed if counting depth of search
    global $n;
    $n++;
    // get the length of passed array
    $l = count($haystack);
    // if length is 0, problem
    if($l <= 0)
    {
        return -1;
    }
    // get the mid element
    $m = (($l+($l%2))/2);
    // if mid >= length (e.g. l=1)
    if($m >= $l)
    {
        $m = $m-1;
    }
    // get the indexed element to compare to the passed element and branch accordingly
    $compare = $haystack[$m];
    switch(true)
    {
        case($compare>$needle):
        {
            // recurse on the lower half
            $new_haystack = array_slice($haystack, 0, $m);
            $c = count($new_haystack);
            $r = binSearch($needle, $new_haystack);
            // return current index - (length of lower half - found index in lower half)
            return $m - ($c - $r);
            break;
        }
        case($compare<$needle):
        {
            // recurse on the upper half
            $new_haystack = array_slice($haystack, $m, ($l-$m));
            $c = count($new_haystack);
            $r = binSearch($needle, $new_haystack);
            // return current position + found index in upper half
            return $m + $r;
            break;
        }
        case($compare==$needle):
        {
            // found it, so return index
            return $m;
            break;
        }
    }
}
?>
Dave C 27-Sep-2011 10:18
Here is a version of binary search that is done via recursion instead of iteration.  Remember that your data needs to be presorted!

<?php
static function Bin_Search(&$needle, &$haystack, $start, $end) {
        if($end < $start)
        {
            return false;
        }

        $mid = (int)(($end - $start) / 2) + $start;
 
        if($haystack[$mid] > $needle)
        {
            return Bin_Search($needle, $haystack, $start, $mid - 1);
        }
        else if($haystack[$mid] < $needle)
        {
            return Bin_Search($needle, $haystack, $mid + 1, $end);
        }
        else
        {
            return true;
        }
}
?>
stefano@takys dot it 14-Jan-2011 10:58
for searching case insensitive better this:

<?php
array_search(strtolower($element),array_map('strtolower',$array));
?>
robert at robert-gonzalez dot com 22-Sep-2010 09:15
I needed a way to find the parent hierarchy of a multidimensional array. Being the rogue that I am, I got to coding before searching the manual and came up with two little functions that will return a parent stack for a first find and a complete parent stack, similar in nature to the solution presented by jette at nerdgirl dot dk without all the extra stuff or use of eval(). ;)

<?php
/**
 * Gets the parent stack of a string array element if it is found within the
 * parent array
 *
 * This will not search objects within an array, though I suspect you could
 * tweak it easily enough to do that
 *
 * @param string $child The string array element to search for
 * @param array $stack The stack to search within for the child
 * @return array An array containing the parent stack for the child if found,
 *               false otherwise
 */
function getParentStack($child, $stack) {
    foreach ($stack as $k => $v) {
        if (is_array($v)) {
            // If the current element of the array is an array, recurse it and capture the return
            $return = getParentStack($child, $v);
           
            // If the return is an array, stack it and return it
            if (is_array($return)) {
                return array($k => $return);
            }
        } else {
            // Since we are not on an array, compare directly
            if ($v == $child) {
                // And if we match, stack it and return it
                return array($k => $child);
            }
        }
    }
   
    // Return false since there was nothing found
    return false;
}

/**
 * Gets the complete parent stack of a string array element if it is found
 * within the parent array
 *
 * This will not search objects within an array, though I suspect you could
 * tweak it easily enough to do that
 *
 * @param string $child The string array element to search for
 * @param array $stack The stack to search within for the child
 * @return array An array containing the parent stack for the child if found,
 *               false otherwise
 */
function getParentStackComplete($child, $stack) {
    $return = array();
    foreach ($stack as $k => $v) {
        if (is_array($v)) {
            // If the current element of the array is an array, recurse it
            // and capture the return stack
            $stack = getParentStackComplete($child, $v);
           
            // If the return stack is an array, add it to the return
            if (is_array($stack) && !empty($stack)) {
                $return[$k] = $stack;
            }
        } else {
            // Since we are not on an array, compare directly
            if ($v == $child) {
                // And if we match, stack it and return it
                $return[$k] = $child;
            }
        }
    }
   
    // Return the stack
    return empty($return) ? false: $return;
}

// TESTING
$array = array(
    'balloon' => array(
        'red' => array(1 => 'Love', 'Valentine', 'Heart',),
        'green' => array(1 => 'Summertime', 'Hope',),
    ),
    'ribbon' => array(
        'yellow' => array(2 => 'Welcome',),
        'red' => array(3 => 'Love', 'Love',),
    ),
);

$s = getParentStack('Love', $array);
$c = getParentStackComplete('Love', $array);
var_dump($s, $c);
?>

Output:

array
  'balloon' =>
    array
      'red' =>
        array
          1 => string 'Love' (length=4)

array
  'balloon' =>
    array
      'red' =>
        array
          1 => string 'Love' (length=4)
  'ribbon' =>
    array
      'red' =>
        array
          3 => string 'Love' (length=4)
          4 => string 'Love' (length=4)
codeslinger at compsalot dot com 02-Oct-2009 09:22
one thing to be very aware of is that array_search() will fail if the needle is a string and the array itself contains values that are mixture of numbers and strings.  (or even a string that looks like a number)

The problem is that unless you specify "strict" the match is done using ==    and in that case any string will match a numeric value of zero which is not what you want.

-----

also, php can lookup an index pretty darn fast.  for many scenarios, it is practical to maintain multiple arrays, one in which the index of the array is the search key and the normal array that contains the data.

<?php

  $normal[$index] = array('key'=>$key, 'data'=>'foo');
  $inverse[$key] = $index;

  //very fast lookup, this beats any other kind of search

  if (array_key_exists($key, $inverse))
  {
    $index = $inverse[$key];
    return $normal[$index];
  }

?>
temporal dot pl at gmail dot com 05-Sep-2009 12:57
Sometimes you need to find a given value in a sorted array or - if not found - detect the place where it should be. After that you can for example split the array into two halves, the  greater and the smaller one.

greenmr, dennis.decoene and php at celerondude had all posted very good binary search functions but these functions all return false if the needle was not found in the haystack. I've tweaked greenmr's code a little:

<?php
function Array_BinarySearch( $needle, $haystack, $comparator , &$probe )
{
    $high = Count( $haystack ) -1;
    $low = 0;
   
    while ( $high >= $low )
    {
        $probe = Floor( ( $high + $low ) / 2 );
        $comparison = $comparator( $haystack[$probe], $needle );
        if ( $comparison < 0 )
        {
            $low = $probe +1;
        }
        elseif ( $comparison > 0 )
        {
            $high = $probe -1;
        }
        else
        {
            return true;
        }
    }
    //The loop ended without a match
    //Compensate for needle greater than highest haystack element
    if($comparator($haystack[count($haystack)-1], $needle) < 0)
    {
        $probe = count($haystack);
    }
    return false;
}
?>

Now, the function returns true if it finds something and false otherwise. If a needle was found, then $probe will contain it's position. Otherwise, $probe will contain position of where the needle would be if it were there :). This is possible because we pass $probe by reference.

Example:

<?php
//ultra-simple comparator :)
function CompareNumbers($obj, $needle)
{
    return $obj - $needle;
}

//use examples
$testArr = array(10, 20, 30, 40, 50);
$res = Array_BinarySearch(30, $testArr, 'CompareNumbers', $probe);
echo (int)$res.' '.$probe.'<br />';
//output is: 1 2 - found at position 2

$res = Array_BinarySearch(45, $testArr, 'CompareNumbers', $probe);
echo (int)$res.' '.$probe.'<br />';
//output is: 0 4 - not found, but it would be at position 4 (between 40 and 45)
 
$res = Array_BinarySearch(-3, $testArr, 'CompareNumbers', $probe);
echo (int)$res.' '.$probe.'<br />';
//output is: 0 0 - not found, but it would be at position 0 (before 10)

$res = Array_BinarySearch(300, $testArr, 'CompareNumbers', $probe);
echo (int)$res.' '.$probe.'<br />';
//output is: 0 5 - not found, but it would be at position 5 (after 50; note, that count($haystack) == 5)
?>

See original greenmr's note for additional details about usage of this binary search: http://php.net/manual/en/function.array-search.php#89413
Nguyen KimKha 23-Aug-2009 07:18
You can remove some values from array, by using unset() and array_search().

<?php

$friends = array( 'Bob', 'Ann', 'Peter' ); // Two persons named 'Bob'
$find = 'Bob';
$key = array_search( $find, $friends ); // Find key of given value
if ($key != NULL || $key !== FALSE) {
    unset($friends[$key]); // remove key from array
}

// Now, $friends = array( 'Ann', 'Peter');

?>
buddel 08-Jun-2009 05:13
the recursive function by tony have a small bug. it failes when a key is 0

here is the corrected version of this helpful function:

<?php
function recursive_array_search($needle,$haystack) {
    foreach($haystack as $key=>$value) {
        $current_key=$key;
        if($needle===$value OR (is_array($value) && recursive_array_search($needle,$value) !== false)) {
            return $current_key;
        }
    }
    return false;
}
?>
tony dot peter at wanadoo dot fr 11-May-2009 09:53
A simple recursive array_search function :

<?php
function recursive_array_search($needle,$haystack) {
    foreach($haystack as $key=>$value) {
        $current_key=$key;
        if($needle===$value OR (is_array($value) && recursive_array_search($needle,$value))) {
            return $current_key;
        }
    }
    return false;
}
?>
n-regen 05-May-2009 07:36
If you only know a part of a value in an array and want to know the complete value, you can use the following function:
<?php
function array_find($needle, $haystack)
{
   foreach ($haystack as $item)
   {
      if (strpos($item, $needle) !== FALSE)
      {
         return $item;
         break;
      }
   }
}
?>
The function returns the complete first value of $haystack that contains $needle.
helenadeus at gmail dot com 25-Jan-2009 10:05
I was trying to use array_search to retrieve all the values that match a given needle, but it turns out only the first match key is returned. I built this little function, which works just like array_search, but returns all the keys that match a given needle instead. The output is an array.

<?php

$haystack = array('a','b','a','b');

$needle = 'a';

print_r(array_search_all($needle, $haystack));

//Output will be
// Array
// (
//         [0]=>1
//         [1]=>3
// )

function array_search_all($needle, $haystack)
{#array_search_match($needle, $haystack) returns all the keys of the values that match $needle in $haystack

    foreach ($haystack as $k=>$v) {
   
        if($haystack[$k]==$needle){
       
           $array[] = $k;
        }
    }
    return ($array);

   
}

?>
azaozz, gmail 21-Dec-2008 02:23
Expanding on the comment by hansen{}cointel.de:

When searching for a string and the array contains 0 (zero), the string is casted to (int) by the type-casting which is always 0 (perhaps the opposite is the proper behaviour, the array value 0 should have been casted to string). That produces unexpected results if strict comparison is not used:

<?php
$a = array(0, "str1", "str2", "str3");
echo "
str1 = ".array_search("str1", $a).",
str2 = ".array_search("str2", $a).",
str3 = ".array_search("str3", $a).",

str1 strict = ".array_search("str1", $a, true).",
str2 strict = ".array_search("str2", $a, true).",
str3 strict = ".array_search("str3", $a, true);
?>

This will return:
str1 = 0, str2 = 0, str3 = 0, str1 strict = 1, str2 strict = 2, str3 strict = 3
dcez at land dot ru 30-Apr-2008 10:15
Simple way to get variable name by using array_search function:

<?php

function varname($var){

    return (isset($var))? array_search($var, $GLOBALS) : false;

}

$boogie = 'tonight';

echo varname($boogie);

?>
andreas dot damm at maxmachine dot de 04-Apr-2008 01:07
Combining syntax of array_search() and functionality of array_keys() to get all key=>value associations of an array with the given search-value:
<?php
function array_search_values( $m_needle, $a_haystack, $b_strict = false){
    return array_intersect_key( $a_haystack, array_flip( array_keys( $a_haystack, $m_needle, $b_strict)));
}
?>

Usage:
<?php
$array1 = array( 'pre'=>'2', 1, 2, 3, '1', '2', '3', 'post'=>2);
print_r( array_search_values( '2', $array1));
print_r( array_search_values( '2', $array1, true));
print_r( array_search_values( 2, $array1, true));
?>

Will return:
array(4) {
    ["pre"] =>
    string(1) "2"
    [1] =>
    int(2)
    [4] =>
    string(1) "2"
    ["post"] =>
    int(2)
}
array(2) {
    ["pre"] =>
    string(1) "2"
    [4] =>
    string(1) "2"
}
array(2) {
    [1] =>
    int(2)
    ["post"] =>
    int(2)
}
kermes [at] thesevens [dot] net 12-Sep-2007 12:09
A variation of previous searches that returns an array of keys that match the given value:

<?php
function array_ksearch($array, $str)
{
    $result = array();
    for($i = 0; $i < count($array); next($array), $i++)
        if(strtolower(current($array)) == strtolower($str))
            array_push($result, key($array);
   
    return $result;
}
?>

Usage would be as follows:
<?php
$testArray = array('one' => 'test1', 'two' => 'test2', 'three' => 'test1', 'four' => 'test2', 'five' => 'test1');
    print_r(array_ksearch($testArray, 'test1'));
?>
robertark at gmail dot com 02-Sep-2007 08:20
A better array_isearch would be to store all results in an array, then return the KEYS stored in $found, such as:

<?php
function array_isearch($str, $array){
  $found = array();
  foreach ($array as $k => $v)
      if (strtolower($v) == strtolower($str)) $found[] = $k;
  return $found;
}
?>

To use, simply have an array to search from then search it, for example:

<?php

function array_isearch($str, $array) {
  $found = array();
  foreach($array as $k => $v)
    if(strtolower($v) == strtolower($str)) $found[] = $k;
  return $found;
}

$stored = "these are an array";
$stored = explode(" ", $stored);

$compare = array("these", "are", "some", "results", "stored", "in", "an", "array");
foreach($stored as $store) {
  $results = array_isearch($store, $compare);
  foreach($results as $key => $result)
    echo "Key: ".$results[$key]."<br />Found: ".$compare[$result]."<br />";
}

?>

Hope this helps :-)

-Rob
mark dot php at mhudson dot net 12-Sep-2006 02:49
I was going to complain bitterly about array_search() using zero-based indexes, but then I realized I should be using in_array() instead.

// if ( isset( $_GET['table'] ) and array_search( $_GET['table'], $valid_tables) ) {  // BAD: fails on first[0] element
// if ( isset( $_GET['table'] ) and ( FALSE !== array_search( $_GET['table'], $valid_tables) ) ) { OK: but wasteful and convoluted
   if ( isset( $_GET['table'] ) and in_array( $_GET['table'], $valid_tables) ) { // BETTER

The essence is this: if you really want to know the location of an element in an array, then use array_search, else if you only want to know whether that element exists, then use in_array()
RichGC 20-Mar-2006 02:54
To expand on previous comments, here are some examples of
where using array_search within an IF statement can go
wrong when you want to use the array key thats returned.

Take the following two arrays you wish to search:

<?php
$fruit_array = array("apple", "pear", "orange");
$fruit_array = array("a" => "apple", "b" => "pear", "c" => "orange");

if ($i = array_search("apple", $fruit_array))
//PROBLEM: the first array returns a key of 0 and IF treats it as FALSE

if (is_numeric($i = array_search("apple", $fruit_array)))
//PROBLEM: works on numeric keys of the first array but fails on the second

if ($i = is_numeric(array_search("apple", $fruit_array)))
//PROBLEM: using the above in the wrong order causes $i to always equal 1

if ($i = array_search("apple", $fruit_array) !== FALSE)
//PROBLEM: explicit with no extra brackets causes $i to always equal 1

if (($i = array_search("apple", $fruit_array)) !== FALSE)
//YES: works on both arrays returning their keys
?>
congaz at yahoo dot dk 10-Mar-2006 04:38
Search a multi-dimensional array on keys!
-------------------------------------------

I needed to search dynamically in a multi-dimen array on keys. I came up with this little neat function. It is so amazingly simple, that I actually didn't think it would work - but it does...

mixed array_searchMultiOnKeys(array, array);

<?php
function array_searchMultiOnKeys($multiArray, $searchKeysArray) {
    // Iterate through searchKeys, making $multiArray smaller and smaller.
    foreach ($searchKeysArray as $keySearch) {
        $multiArray = $multiArray[$keySearch];
        $result = $multiArray;
    }
   
    // Check $result.
    if (is_array($multiArray)) {
        // An array was found at the end of the search. Return true.
        $result = true;
    }
    else if ($result == '') {
        // There was nothing found at the end of the search. Return false.
        $result = false;
    }

    return $result;
// End of function,
}

// --- Test array_searchMultiOnKeys ---
$multiArray['webpages']['downloads']['music'] = 1;
$multiArray['webpages']['downloads']['pressmaterial'] = 5;
$multiArray['webpages']['links'] = 7;

array_searchMultiOnKeys($multiArray, array('webpages', 'links')); // returns 7.
array_searchMultiOnKeys($multiArray, array('webpages', 'downloads')); // returns true.
array_searchMultiOnKeys($multiArray, array('webpages', 'downloads', 'software')); // returns false.

?>

$multiArray / $searchKeysArray can be any size.

Happy hacking...
09-Feb-2006 03:26
may be good to take note of PHP's mind-boggling 'fuzzy' (vulgo "magic type-casting") comparison features not only in using the results, but also in the search, too:
<?php
$a=array("a","b",0,"c","d");
echo "a: ".array_search("a",$a);
echo "b: ".array_search("b",$a);
echo "c: ".array_search("c",$a);
echo "d: ".array_search("d",$a);
echo "0: ".array_search("0",$a);
echo "x: ".array_search("x",$a);
echo "1: ".array_search("1",$a);
?>
will result in:
a: 0, b: 1, c: 2, d: 2, 0: 2, x: 2, 1: false

as from "c" on, the first match found in $a is "0", as any string compared to an int is automatically cast to (int)0.
22-Oct-2004 02:01
There is no function to count the occurences of needle in haystack, so I made my own one...

<?php
function array_match($needle, $haystack)
{
    if( !is_array($haystack) ) return false;
   
    $i = 0;
    while( (in_array( $needle, $haystack )) != FALSE )
    {
        $i++;
        $haystack[array_search($needle, $haystack)] = md5($needle);
        reset($haystack);
    }
   
    return $i;
}
?>

I know it's a bit crappy, but don't ask me too much, I'm still only 13... ;)
dennis dot decoene at removthis dot moveit dot be 17-Jan-2004 07:41
It has been said before: array_search is VERY slow. Everyone knows binary search is fast by design. Here is an implementation.

<?php
$arr=array(1,3,5,7,9,10,11,13);
$searchfor = 6;
echo binsearch($searchfor, $arr);

/**
 * @return integer
 * @param var $needle
 * @param array $haystack
 * @desc Feed a sorted array to $haystack and a value to search for to $needle.
             It will return false if not found or the index where it was found.
             This function is superfast. Try an array with 50.000 elements and search for something,
             you will be amazed.
*/
function binsearch($needle, $haystack)
{
    $high = count($haystack);
    $low = 0;
   
    while ($high - $low > 1){
        $probe = ($high + $low) / 2;
        if ($haystack[$probe] < $needle){
            $low = $probe;
        }else{
            $high = $probe;
        }
    }

    if ($high == count($haystack) || $haystack[$high] != $needle) {
        return false;
    }else {
        return $high;
    }
}
?>
cue at openxbox dot com 10-Jun-2003 04:50
If you are using the result of array_search in a condition statement, make sure you use the === operator instead of == to test whether or not it found a match.  Otherwise, searching through an array with numeric indicies will result in index 0 always getting evaluated as false/null.  This nuance cost me a lot of time and sanity, so I hope this helps someone.  In case you don't know what I'm talking about, here's an example:

<?php
$code = array("a", "b", "a", "c", "a", "b", "b"); // infamous abacabb mortal kombat code :-P

// this is WRONG
while (($key = array_search("a", $code)) != NULL)
{
 // infinite loop, regardless of the unset
 unset($code[$key]);
}

// this is _RIGHT_
while (($key = array_search("a", $code)) !== NULL)
{
 // loop will terminate
 unset($code[$key]);
}
?>
swbrown at ucsd dot edu 02-May-2002 10:18
Be absolutely sure to check that your code that uses array_search now checks for 'false' too if you upgrade to PHP 4.2.0!

I was using array_search in my page authentication routines and this change had the fun side-effect of causing my code to always think a user had full permissions!  It was letting anyone click through to our installation of phpMyAdmin.  Not good indeed!