public function where($firstColumn, $operator, $secondColumn, $boolean = 'and') {
		return $this->on($firstColumn, $operator, $secondColumn, $boolean, true);
	}
public function where($firstColumn, $operator, $secondColumn, $boolean = 'and') {
		return $this->on($firstColumn, $operator, $secondColumn, $boolean, true);
	}
public function where ( $ firstColumn , $ operator , $ secondColumn , $ boolean = 'and' ) { return $ this -> on ( $ firstColumn , $ operator , $ secondColumn , $ boolean , true ) ; }
Add an "on where" clause to the join.

@param string $firstColumn
@param string $operator
@param string $second
@param string $boolean
@return \queryBuilder\JoinClause
Add an on where clause to the join .