array_search($needle, array_column($array, 'key')); //Example $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'));