你可能意思是稍微修改（否则我有语法错误）：

You probably mean it with a slight modification (I got a syntax error otherwise):

<?php
class Singleton {
    public static function getInstance() {
        static $instance;
        if ($instance === null)
            $instance = new Singleton();
        xdebug_debug_zval('instance');
        return $instance;
    }
    private function __construct() { }
}
$a = Singleton::getInstance();
xdebug_debug_zval('a');
$b = Singleton::getInstance();
xdebug_debug_zval('b');

这给出：

实例： i>（refcount = 2，is_ref = 1），
对象（ Singleton ）[ 1 ]

instance: (refcount=2, is_ref=1), object(Singleton)[1]

a：（refcount = 1，is_ref = 0），
i> Singleton ）[ 1 ]

a: (refcount=1, is_ref=0), object(Singleton)[1]

实例：（refcount = 2，is_ref = 1 ），
对象（ Singleton ）[ 1 ]

instance: (refcount=2, is_ref=1), object(Singleton)[1]

b：（refcount = 1，is_ref = 0），
对象（ Singleton ）[ i> 1 ]

b: (refcount=1, is_ref=0), object(Singleton)[1]

所以它有缺点，每次调用都会创建一个新的zval。这不是特别严重，所以如果你喜欢它，请继续。

So it has the disadvantage a new zval will be created on each call. This is not particularly serious, so if you prefer it, go ahead.

zval分离***的原因是在 getInstance ， $ instance 是一个引用（在 =& 的意义上，它有引用计数2（一个用于方法中的符号，另一个用于静态存储）由于 getInstance 不会通过引用返回，所以zval必须分开 - 对于返回，创建一个新的引用计数1，引用标志清除。

The reason a zval separation is forced is that inside getInstance, $instance is a reference (in the sense of =&, and it has reference count 2 (one for the symbol inside the method, another for the static storage). Since getInstance doesn't return by reference, the zval must be separated -- for the return, a new one is created with reference count 1 and the reference flag clear.