在 PHP 中声明一个不必要的变量会消耗内存吗? [英] Does declaring an unnecessary variable in PHP consumes memory?

问题描述

我通常在 PHP 中执行此操作以获得更好的可读性，但我不知道它是否消耗内存或有任何其他问题?假设我有这个代码:

I usually do this in PHP for better readability but I don't know if it consumes memory or has any other issues? Let's say I have this code:

$user = getUser(); // getUser() will return an array

我可以做到:

$email = $user["email"];
sendEmail($email);

不声明变量 $email 我可以这样做:

Without declaring the variable $email I could do:

sendEmail($user["email"]);

哪个更好?考虑到这只是一个非常简单的例子.

Which one is better? Consider that this is just a very simple example.

推荐答案

不要为了节省几个字节而降低代码的可读性.即使 $email 是一个 100 MB 的字符串，这也不会为您节省更多，因为 PHP 在内部使用了写入时复制机制:内容 除非您更改变量，否则不会复制它.

Don't make your code less readable just to save a few bytes. And this will not save you more, even if $email is a 100 MB string, because internally PHP uses the copy on write mechanism: The content of a variable is not copied unless you change it.

示例:

$a = str_repeat('x', 100000000); // Memory used ~ 100 MB
$b = $a;                         // Memory used ~ 100 MB
$b = $b . 'x';                   // Memory used ~ 200 MB

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