我正试图用Doctrine的查询生成器构建一个动态查询。假设我还想在下面选择一个结束时间（只有输入了一个）。我该如何有条件地将其添加到声明中？
$query = $this->getEntityManager()->createQueryBuilder()
->select('m')
->from($this->getEntityName(), 'm')
->where("m.start > '" . date('Y-m-d H:i:s', strtotime($start)) . "'")
->getQuery();
我会这样做：
// first, create the query builder
$qb = $this->getEntityManager()->createQueryBuilder()
->select('m')
->from($this->getEntityName(), 'm')
;
// add the default condition
$conditions = array(
$qb->expr()->gt('m.start', date('Y-m-d H:i:s', strtotime($start)));
);
// put your condition here
if (isset($end)) {
$conditions[] = $qb->expr()->lt('m.end', date('Y-m-d H:i:s', strtotime($end)));
}
// convert the conditions to an AND clause
$conditions = call_user_func_array(array($qb, 'andX'), $conditions);
// add the WHERE clause
$qb->where($conditions);
// get the query
$query = $qb->getQuery();