php - Null 有课吗？

Question

涉及 Symfony 1.4 和 Propel，但我不确定它们会导致下面描述的奇怪行为。

$this->_parent = TestPeer::retrieveByPK($this->getParentId());
var_dump(get_class($this->_parent), $this->_parent);

打印出 'Test' 和 'null'。

怎么会这样？

附言

1/$this->getParentId()返回整数，DB中没有对应的记录，所以$this->_parent应该为null。

2/php 5.5.6, xdebug, opcache

Answer 1

引自 The PHP Manual对于 get_class:

5.3.0 NULL became the default value for object, so passing NULL to object now has the same result as not passing any value.

连同:

Returns the name of the class of which object is an instance. Returns FALSE if object is not an object.

If object is omitted when inside a class, the name of that class is returned.

...意味着当传递 null 时，您将获得包含调用的类的名称。