public function exists()
    {
        foreach (func_get_args() as $value) {
            if (!in_array($value, $this->collection)) {
                return false;
            }
        }

        return true;
    }
public function exists()
    {
        foreach (func_get_args() as $value) {
            if (!in_array($value, $this->collection)) {
                return false;
            }
        }

        return true;
    }
public function exists ( ) { foreach ( func_get_args ( ) as $ value ) { if ( ! in_array ( $ value , $ this -> collection ) ) { return false ; } } return true ; }
Checks whether value exists in a stack

@param string $value [...]
@return boolean
Checks whether value exists in a stack