Doctrine\MongoDB\Query\Builder::exists PHP Method

Specify $exists criteria for the current field.

See also: Expr::exists()

See also: http://docs.mongodb.org/manual/reference/operator/exists/

public exists ( boolean $bool )
$bool	boolean

    public function exists($bool)
    {
        $this->expr->exists((bool) $bool);
        return $this;
    }