PHP析構方法 __destruct() 不觸發的兩個解決方法

本篇文章主要介紹PHP 析構方法 __destruct() 不觸發的兩個解決方法。

有時在PHP 裡類別循環引用時，會導致__destruct() 不觸發的問題，先上問題代碼：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Proxy&#39;);
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Test&#39;);
    }
}
 
$test = new Test;
unset($test);
 
echo &#39;no __destruct, wait 3s&#39;, PHP_EOL;
 
sleep(3);
 
echo &#39;__destruct now:&#39;, PHP_EOL;

如上程式碼，執行unset($test)時，不會觸發__destruct()，因為有了循環引用。

再看下面的解決方法1的程式碼：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Proxy&#39;);
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Test&#39;);
    }
 
    public function close()
    {
        $this->proxy = null;
    }
}
 
$test = new Test;
$test->close();
 
echo &#39;__destruct now:&#39;, PHP_EOL;
 
unset($test);
 
sleep(3);
 
echo &#39;no operation&#39;, PHP_EOL;

上面的程式碼，在unset之前，將Test類別中的proxy設為null，然後再unset，就可以觸發__destruct ()了。

當然，你也可以手動gc（解決方法2）：

<?php
class Proxy
{
    private $object;
 
    public function __construct($object)
    {
        $this->object = $object;
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Proxy&#39;);
    }
}
 
class Test
{
    private $proxy;
 
    public function __construct()
    {
        $this->proxy = new Proxy($this);
    }
 
    public function __destruct()
    {
        var_dump(&#39;__destruct:Test&#39;);
    }
}
 
$test = new Test;
unset($test);
 
echo &#39;__destruct now:&#39;, PHP_EOL;
gc_collect_cycles();
 
sleep(3);
 
echo &#39;no operation&#39;, PHP_EOL;

希望對需要的朋友有幫助！

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