public static function findKey(array $arr, \Closure $predicate){
		foreach($arr as $k => $v){
			if($predicate($v, $k)){
				return $k;
			}
		}
		return null;
	}
public static function findKey(array $arr, \Closure $predicate){
		foreach($arr as $k => $v){
			if($predicate($v, $k)){
				return $k;
			}
		}
		return null;
	}
public static function findKey ( array $ arr , \ Closure $ predicate ) { foreach ( $ arr as $ k => $ v ) { if ( $ predicate ( $ v , $ k ) ) { return $ k ; } } return null ; }
Returns the key for the element which passes the given predicate function

@param array $arr
@param \Closure $predicate
@return mixed|null null is returned if no match was found
Returns the key for the element which passes the given predicate function