Check if a specific value exists at a specific key in any subarray of a multidimensional array

Nothing will be faster than a simple loop. You can mix-and-match some array functions to do it, but they'll just be implemented as a loop too.

function whatever($array, $key, $val) {    foreach ($array as $item)        if (isset($item[$key]) && $item[$key] == $val)            return true;    return false;}

Here is an updated version of Dan Grossman's answer which will cater for multidimensional arrays (what I was after):

function find_key_value($array, $key, $val){    foreach ($array as $item)    {        if (is_array($item) && find_key_value($item, $key, $val)) return true;        if (isset($item[$key]) && $item[$key] == $val) return true;    }    return false;}

** PHP >= 5.5

simply u can use this

$key = array_search(40489, array_column($userdb, 'uid'));

Let's suppose this multi dimensional array:

$userdb=Array((0) => Array    (        (uid) => '100',        (name) => 'Sandra Shush',        (url) => 'urlof100'    ),(1) => Array    (        (uid) => '5465',        (name) => 'Stefanie Mcmohn',        (pic_square) => 'urlof100'    ),(2) => Array    (        (uid) => '40489',        (name) => 'Michael',        (pic_square) => 'urlof40489'    ));$key = array_search(40489, array_column($userdb, 'uid'));