/**
* Add an "on" clause to the join.
*
* @param string $first
* @param string $operator
* @param string $second
* @param string $boolean
* @param bool $where
* @return \Illuminate\Database\Query\JoinClause
*/
public function on($first, $operator, $second, $boolean = 'and', $where = false)
{
$this->clauses[] = compact('first', 'operator', 'second', 'boolean', 'where');
if ($where) {
$this->query->addBinding($second);
}
return $this;
}