PHP:在循环内或外实例化类在占用内存上有很大的区别

先来一个test1.php

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class ABC{
    public $numBox = array();
    public function ddd(){
        for($i = 1; $i <= 600; $i++){
            $this->numBox[] = mt_rand(1,1000000);
        }
        echo 'Now memory_get_usage: '.memory_get_usage().'<br />';
    }
}
$instance = new ABC();
for($i = 0; $i< 50; $i++){
    $instance->ddd();
}

这是test1.php的运行结果

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Now memory_get_usage: 422728
Now memory_get_usage: 474824
Now memory_get_usage: 522824
Now memory_get_usage: 579024
Now memory_get_usage: 627024
Now memory_get_usage: 675024
Now memory_get_usage: 739408
Now memory_get_usage: 787416
Now memory_get_usage: 835416
Now memory_get_usage: 883416
Now memory_get_usage: 931416
Now memory_get_usage: 979416
Now memory_get_usage: 1027416
..................

再来一个test2.php

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class ABC{
    public $numBox = array();
    public function ddd(){
        for($i=1; $i<=600; $i++){
            $this->numBox[] = mt_rand(1,1000000);
        }
        echo 'Now memory_get_usage: '.memory_get_usage().'<br />';
    }
}
for($i = 0; $i < 50; $i++){
    $instance = new ABC();
    $instance->ddd();
}

这是test2.php的运行结果

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Now memory_get_usage: 422728
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
Now memory_get_usage: 422712
............................