Doctrine\ORM\Query\Parser::NullComparisonExpression PHP Method

    public function NullComparisonExpression()
    {
        if ($this->_lexer->isNextToken(Lexer::T_INPUT_PARAMETER)) {
            $this->match(Lexer::T_INPUT_PARAMETER);
            $expr = new AST\InputParameter($this->_lexer->token['value']);
        } else {
            $expr = $this->SingleValuedPathExpression();
        }

        $nullCompExpr = new AST\NullComparisonExpression($expr);
        $this->match(Lexer::T_IS);

        if ($this->_lexer->isNextToken(Lexer::T_NOT)) {
            $this->match(Lexer::T_NOT);
            $nullCompExpr->not = true;
        }

        $this->match(Lexer::T_NULL);

        return $nullCompExpr;
    }