public function hasKey($target)
    {
        foreach ($this->collection as $group => $hashMap) {
            if (array_key_exists($target, $hashMap)) {
                return true;
            }
        }

        // By default
        return false;
    }
public function hasKey($target)
    {
        foreach ($this->collection as $group => $hashMap) {
            if (array_key_exists($target, $hashMap)) {
                return true;
            }
        }

        // By default
        return false;
    }
public function hasKey ( $ target ) { foreach ( $ this -> collection as $ group => $ hashMap ) { if ( array_key_exists ( $ target , $ hashMap ) ) { return true ; } } // By default return false ; }
Checks whether key in collection exist

@param string $target
@return boolean
Checks whether key in collection exist