protected function _getPrimaryKey()
    {
        if (!$this->_primaryKey) {
            $primaryKey = (array)$this->_table->getPrimaryKey();
            $this->_primaryKey = $primaryKey[0];
        }

        return $this->_primaryKey;
    }
protected function _getPrimaryKey()
    {
        if (!$this->_primaryKey) {
            $primaryKey = (array)$this->_table->getPrimaryKey();
            $this->_primaryKey = $primaryKey[0];
        }

        return $this->_primaryKey;
    }
protected function _getPrimaryKey ( ) { if ( ! $ this -> _primaryKey ) { $ primaryKey = ( array ) $ this -> _table -> getPrimaryKey ( ) ; $ this -> _primaryKey = $ primaryKey [ 0 ] ; } return $ this -> _primaryKey ; }
Returns a single string value representing the primary key of the attached table

@return string
Returns a single string value representing the primary key of the attached table