问题
Is a class destructor in PHP predictable? When is the destructor called?
Like in many languages, will a class destructor be called as soon as the object goes out of scope?
回答1:
PHP 5 introduces a destructor concept similar to that of other object-oriented languages, such as C++. The destructor method will be called as soon as all references to a particular object are removed or when the object is explicitly destroyed or in any order in shutdown sequence.
http://php.net/manual/en/language.oop5.decon.php
回答2:
It's called when the first of these conditions are met:
- The reference count of the object goes to 0 (these usually happens when the object has no more variables that reference it -- they were unset or went out of scope --, but it can happen later, as an object may be referenced by something other than a variable -- in fact, the reference count is just a number and can be manipulated in an arbitrary way).
- When using PHP 5.3, when the garbage collector detects the positive reference count is due to circular references.
- Otherwise, when the script finishes cleanly.
In short, you should not rely on it always being called, because the script may not finish cleanly.
来源：https://stackoverflow.com/questions/3325979/is-destructor-in-php-predictable