function delete($key) {
        $this->data[$key] = null;
        unset($this->data[$key]);
        return $this;
    }
function delete($key) {
        $this->data[$key] = null;
        unset($this->data[$key]);
        return $this;
    }
function delete ( $ key ) { $ this -> data [ $ key ] = null ; unset ( $ this -> data [ $ key ] ) ; return $ this ; }
Removes an item from the collection by its key.
@param mixed  $key
@return $this
Removes an item from the collection by its key .