PHP Multidimensional Array Searching (Find key by specific value)

Another poossible solution is based on the array_search() function. You need to use PHP 5.5.0 or higher.

Example

$userdb=Array((0) => Array    (        (uid) => '100',        (name) => 'Sandra Shush',        (url) => 'urlof100'    ),(1) => Array    (        (uid) => '5465',        (name) => 'Stefanie Mcmohn',        (pic_square) => 'urlof100'    ),(2) => Array    (        (uid) => '40489',        (name) => 'Michael',        (pic_square) => 'urlof40489'    ));$key = array_search(40489, array_column($userdb, 'uid'));echo ("The key is: ".$key);//This will output- The key is: 2

Explanation

The function array_search() has two arguments. The first one is the value that you want to search. The second is where the function should search. The function array_column() gets the values of the elements which key is 'uid'.

Summary

So you could use it as:

array_search('breville-one-touch-tea-maker-BTM800XL', array_column($products, 'slug'));

or, if you prefer:

// define functionfunction array_search_multidim($array, $column, $key){    return (array_search($key, array_column($array, $column)));}// use itarray_search_multidim($products, 'slug', 'breville-one-touch-tea-maker-BTM800XL');

The original example(by xfoxawy) can be found on the DOCS.
The array_column() page.

Update

Due to Vael comment I was curious, so I made a simple test to meassure the performance of the method that uses array_search and the method proposed on the accepted answer.

I created an array which contained 1000 arrays, the structure was like this (all data was randomized):

[      {            "_id": "57fe684fb22a07039b3f196c",            "index": 0,            "guid": "98dd3515-3f1e-4b89-8bb9-103b0d67e613",            "isActive": true,            "balance": "$2,372.04",            "picture": "http://placehold.it/32x32",            "age": 21,            "eyeColor": "blue",            "name": "Green",            "company": "MIXERS"      },...]

I ran the search test 100 times searching for different values for the name field, and then I calculated the mean time in milliseconds. Here you can see an example.

Results were that the method proposed on this answer needed about 2E-7 to find the value, while the accepted answer method needed about 8E-7.

Like I said before both times are pretty aceptable for an application using an array with this size. If the size grows a lot, let's say 1M elements, then this little difference will be increased too.

Update II

I've added a test for the method based in array_walk_recursive which was mentionend on some of the answers here. The result got is the correct one. And if we focus on the performance, its a bit worse than the others examined on the test. In the test, you can see that is about 10 times slower than the method based on array_search. Again, this isn't a very relevant difference for the most of the applications.

Update III

Thanks to @mickmackusa for spotting several limitations on this method:

• This method will fail on associative keys.
• This method will only work on indexed subarrays (starting from 0 and have consecutively ascending keys).

Very simple:

function myfunction($products, $field, $value){   foreach($products as $key => $product)   {      if ( $product[$field] === $value )         return $key;   }   return false;}

This class method can search in array by multiple conditions:

class Stdlib_Array{    public static function multiSearch(array $array, array $pairs)    {        $found = array();        foreach ($array as $aKey => $aVal) {            $coincidences = 0;            foreach ($pairs as $pKey => $pVal) {                if (array_key_exists($pKey, $aVal) && $aVal[$pKey] == $pVal) {                    $coincidences++;                }            }            if ($coincidences == count($pairs)) {                $found[$aKey] = $aVal;            }        }        return $found;    }    }// Example:$data = array(    array('foo' => 'test4', 'bar' => 'baz'),    array('foo' => 'test',  'bar' => 'baz'),    array('foo' => 'test1', 'bar' => 'baz3'),    array('foo' => 'test',  'bar' => 'baz'),    array('foo' => 'test',  'bar' => 'baz4'),    array('foo' => 'test4', 'bar' => 'baz1'),    array('foo' => 'test',  'bar' => 'baz1'),    array('foo' => 'test3', 'bar' => 'baz2'),    array('foo' => 'test',  'bar' => 'baz'),    array('foo' => 'test',  'bar' => 'baz'),    array('foo' => 'test4', 'bar' => 'baz1'));$result = Stdlib_Array::multiSearch($data, array('foo' => 'test4', 'bar' => 'baz1'));var_dump($result);

Will produce:

array(2) {  [5]=>  array(2) {    ["foo"]=>    string(5) "test4"    ["bar"]=>    string(4) "baz1"  }  [10]=>  array(2) {    ["foo"]=>    string(5) "test4"    ["bar"]=>    string(4) "baz1"  }}