如何使用if条件在“;create_query";在符号2中


How can i use if condition in "create_query" in symfony2

在我的表单生成器中,我正在尝试使用这个

'query_builder' => function(EntityRepository $er) {
                                 return $er->createQueryBuilder('u')
                                 if(var)                                     
                                  ->where('u.id = 3')
'query_builder' => function(EntityRepository $er) {
    $qb = $er->createQueryBuilder('u');
    if ($someCondition) {
        $qb->where('u.id = 3');
    }
    return $qb;
}