public function offsetExists($key)
    {
        if(isset($this->data[$key])){
            return new self($this->data[$key]);
        }

        return false;
    }
public function offsetExists($key)
    {
        if(isset($this->data[$key])){
            return new self($this->data[$key]);
        }

        return false;
    }
public function offsetExists ( $ key ) { if ( isset ( $ this -> data [ $ key ] ) ) { return new self ( $ this -> data [ $ key ] ) ; } return false ; }
Determine if a given offset exists

/!\ different from has method

@param  string  $key
@return bool
Determine if a given offset exists