Doctrine orm DQL扩展不工作

在我的项目中，我有以下DQL扩展

namespace Freedom\Doctrine\ORM\AST\Functions;

use Doctrine\ORM\Query\AST\Functions\FunctionNode;
use Doctrine\ORM\Query\Lexer;
use Doctrine\ORM\Query\Parser;
use Doctrine\ORM\Query\SqlWalker;

/**
 * MatchAgainstFunction ::=
 *  "MATCH" "(" StateFieldPathExpression {"," StateFieldPathExpression}* ")" "AGAINST" "("
 *      StringPrimary ["BOOLEAN"] ["EXPAND"] ")"
 */
class MatchAgainstFunction extends FunctionNode
{

    /** @var array list of \Doctrine\ORM\Query\AST\PathExpression */
    protected $pathExp = null;

    /** @var string */
    protected $against = null;

    /** @var boolean */
    protected $booleanMode = false;

    /** @var boolean */
    protected $queryExpansion = false;

    public function parse(Parser $parser)
    {
        // match
        $parser->match(Lexer::T_IDENTIFIER);
        $parser->match(Lexer::T_OPEN_PARENTHESIS);

        // first Path Expression is mandatory
        $this->pathExp = array();
        $this->pathExp[] = $parser->StateFieldPathExpression();

        // Subsequent Path Expressions are optional
        $lexer = $parser->getLexer();
        while ($lexer->isNextToken(Lexer::T_COMMA)) {
            $parser->match(Lexer::T_COMMA);
            $this->pathExp[] = $parser->StateFieldPathExpression();
        }

        $parser->match(Lexer::T_CLOSE_PARENTHESIS);

        // against
        if (strtolower($lexer->lookahead['value']) !== 'against') {
            $parser->syntaxError('against');
        }

        $parser->match(Lexer::T_IDENTIFIER);
        $parser->match(Lexer::T_OPEN_PARENTHESIS);
        $this->against = $parser->StringPrimary();

        if (strtolower($lexer->lookahead['value']) === 'boolean') {
            $parser->match(Lexer::T_IDENTIFIER);
            $this->booleanMode = true;
        }

        if (strtolower($lexer->lookahead['value']) === 'expand') {
            $parser->match(Lexer::T_IDENTIFIER);
            $this->queryExpansion = true;
        }

        $parser->match(Lexer::T_CLOSE_PARENTHESIS);
    }

    public function getSql(SqlWalker $walker)
    {
        $fields = array();
        foreach ($this->pathExp as $pathExp) {
            $fields[] = $pathExp->dispatch($walker);
        }

        $against = $walker->walkStringPrimary($this->against)
                . ($this->booleanMode ? ' IN BOOLEAN MODE' : '')
                . ($this->queryExpansion ? ' WITH QUERY EXPANSION' : '');

        return sprintf('MATCH (%s) AGAINST (%s)', implode(', ', $fields), $against);
    }

}

在我的DQL中，我有

$builder->andWhere('MATCH (t.title) AGAINST (:title)')
        ->setParameter('title', $param);

我发现了错误

[语法错误]第0行，第204列：错误：预期=，=，！=，有“命令”

我在DQL中的andWhere之后有一个orderBy

---

有人知道为什么条令要寻找比较运算符吗？

我已经弄明白了。我将DQL更改为

$builder->andWhere('MATCH (t.title) AGAINST (:title BOOLEAN) > 0')
        ->setParameter('title', $param);

现在它似乎正在发挥作用