Get key of multidimensional array?

This is quite simple, you just need to use array_keys():

$keys = array_keys($array); 

See it working

EDIT For your search task, this function should do the job:

function array_search_inner ($array, $attr, $val, $strict = FALSE) { // Error is input array is not an array if (!is_array($array)) return FALSE; // Loop the array foreach ($array as $key => $inner) { // Error if inner item is not an array (you may want to remove this line) if (!is_array($inner)) return FALSE; // Skip entries where search key is not present if (!isset($inner[$attr])) continue; if ($strict) { // Strict typing if ($inner[$attr] === $val) return $key; } else { // Loose typing if ($inner[$attr] == $val) return $key; } } // We didn't find it return NULL; } // Example usage $key = array_search_inner($array, 'id', 9); 

The fourth parameter $strict, if TRUE, will use strict type comparisons. So 9 will not work, you would have to pass '9', since the values are stored as strings. Returns the key of the first occurence of a match, NULL if the value is not found, or FALSE on error. make sure to use a strict comparison on the return value, since 0, NULL and FALSE are all possible return values and they will all evaluate to 0 if using loose integer comparisons.