PHP析构方法 __destruct() 不触发的两个解决办法

有时候在 PHP 里类循环引用时，会导致 __destruct() 不触发的问题，先上问题代码：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Proxy');
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Test');
    }
}
 
$test = new Test;
unset($test);
 
echo 'no __destruct, wait 3s', PHP_EOL;
 
sleep(3);
 
echo '__destruct now:', PHP_EOL;

如上代码，运行unset($test)时，不会触发__destruct()，因为有了循环引用。

再看下面的解决方法1的代码：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Proxy');
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Test');
    }
 
    public function close()
    {
        $this->proxy = null;
    }
}
 
$test = new Test;
$test->close();
 
echo '__destruct now:', PHP_EOL;
 
unset($test);
 
sleep(3);
 
echo 'no operation', PHP_EOL;

上面的代码，在unset之前，将Test类中的proxy设为null，然后再unset，就可以触发__destruct()了。

当然，你也可以手动gc（解决方法2）：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Proxy');
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump('__destruct:Test');
    }
}
 
$test = new Test;
unset($test);
 
echo '__destruct now:', PHP_EOL;
gc_collect_cycles();
 
sleep(3);
 
echo 'no operation', PHP_EOL;

希望对需要的朋友有所帮助！

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