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

    public function Join()
    {
        // Check Join type
        $joinType = AST\Join::JOIN_TYPE_INNER;

        if ($this->_lexer->isNextToken(Lexer::T_LEFT)) {
            $this->match(Lexer::T_LEFT);

            // Possible LEFT OUTER join
            if ($this->_lexer->isNextToken(Lexer::T_OUTER)) {
                $this->match(Lexer::T_OUTER);
                $joinType = AST\Join::JOIN_TYPE_LEFTOUTER;
            } else {
                $joinType = AST\Join::JOIN_TYPE_LEFT;
            }
        } else if ($this->_lexer->isNextToken(Lexer::T_INNER)) {
            $this->match(Lexer::T_INNER);
        }

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

        $joinPathExpression = $this->JoinAssociationPathExpression();

        if ($this->_lexer->isNextToken(Lexer::T_AS)) {
            $this->match(Lexer::T_AS);
        }

        $token = $this->_lexer->lookahead;
        $aliasIdentificationVariable = $this->AliasIdentificationVariable();

        // Verify that the association exists.
        $parentClass = $this->_queryComponents[$joinPathExpression->identificationVariable]['metadata'];
        $assocField = $joinPathExpression->associationField;

        if ( ! $parentClass->hasAssociation($assocField)) {
            $this->semanticalError(
                "Class " . $parentClass->name . " has no association named '$assocField'."
            );
        }

        $targetClassName = $parentClass->associationMappings[$assocField]['targetEntity'];

        // Building queryComponent
        $joinQueryComponent = array(
            'metadata'     => $this->_em->getClassMetadata($targetClassName),
            'parent'       => $joinPathExpression->identificationVariable,
            'relation'     => $parentClass->getAssociationMapping($assocField),
            'map'          => null,
            'nestingLevel' => $this->_nestingLevel,
            'token'        => $token
        );
        $this->_queryComponents[$aliasIdentificationVariable] = $joinQueryComponent;

        // Create AST node
        $join = new AST\Join($joinType, $joinPathExpression, $aliasIdentificationVariable);

        // Check for ad-hoc Join conditions
        if ($this->_lexer->isNextToken(Lexer::T_WITH)) {
            $this->match(Lexer::T_WITH);
            $join->conditionalExpression = $this->ConditionalExpression();
        }

        return $join;
    }