PHP 在从变量定义变量并将对象实例转换为另一个变量时是否占用 RAM? [英] Does PHP take RAM when defining variable from variable and taking instance of object to another variable?

问题描述

如果我有这个代码

<?php
$array = array();
for ($i=1;$i<100000;$i++){
    $array[$i] = md5(rand(0,9999999999999999));
}

$array2 = $array;

$array 大约需要 0.5MB RAM，比方说.PHP proccess 使用 $array2 = $array; 需要大约 1.0MB RAM 吗?在这种情况下

$array takes about 0.5MB RAM, let's say. Does PHP proccess take about 1.0MB RAM with $array2 = $array; ? and in this case

<?php
class rand{
    public $array;
    function rand(){
        $this->array = array();
        for ($i=1;$i<100000;$i++){
            $this->array[$i] = md5(rand(0,9999999999999999));
        }

    }
}

$class = new rand();
$class2 = $class;

$class 大约需要 0.5MB RAM，比方说.使用 $class2 = $class 时 PHP 进程是否需要 1.0MB?

$class takes about 0.5MB RAM, let's say . Does PHP proccess take 1.0MB with $class2 = $class?

是一样的吗?

测试:

• 首先
• 第二

推荐答案

这是参考部分的 PHP 手册警告的:引擎足够智能.设置 $array2 = $array; 不会 导致重复存储，因为 PHP 认识到它们仍然相同.但是，在此之后尝试 $array[2] = 'something;' .PHP 检测到差异，只有 then 会复制这些值.

This is what the PHP manual in the reference section warns about: the Engine is smart enough. Setting the $array2 = $array; does not cause duplicate storage, as PHP recognizes they are still both the same. However, try a $array[2] = 'something;' after that. PHP detects the difference, and only then will copy the values.

<?php
$array = array();
for ($i=1;$i<100000;$i++){
    $array[$i] = md5(rand(0,9999999999999999));
}
echo memory_get_usage().PHP_EOL;
$array2 = $array;
echo memory_get_usage().PHP_EOL;
$array['foo'] = 'bar';
echo memory_get_usage().PHP_EOL;
//17252052
//17252156
//23776652

类在默认情况下是引用，只有一个 clone $object 会在 PHP >= 5 中产生 2 个对象.

Classes are references by default, and only a clone $object would result in 2 objects in PHP >= 5.

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