诊断内存泄漏-允许的内存大小已耗尽#个字节 [英] Diagnosing Memory Leaks - Allowed memory size of # bytes exhausted

问题描述

我遇到了可怕的错误消息，可能是经过艰苦的努力，PHP内存不足:

I've encountered the dreaded error-message, possibly through-painstaking effort, PHP has run out of memory:

在第123行的file.php中允许的####个字节的内存大小用尽(试图分配####个字节)

Allowed memory size of #### bytes exhausted (tried to allocate #### bytes) in file.php on line 123

提高限额

如果您知道自己在做什么并且想要增加限制，请参见当心！您可能只是在解决症状，而没有解决问题！

Beware! You may only be solving the symptom and not the problem!

错误消息指向带有循环的一行，我认为这是正在泄漏或不必要地累积内存.我在每次迭代结束时都打印了memory_get_usage()语句，可以看到该数字缓慢增长直到达到极限:

The error message points to a line withing a loop that I believe to be leaking, or needlessly-accumulating, memory. I've printed memory_get_usage() statements at the end of each iteration and can see the number slowly grow until it reaches the limit:

foreach ($users as $user) {
    $task = new Task;
    $task->run($user);
    unset($task); // Free the variable in an attempt to recover memory
    print memory_get_usage(true); // increases over time
}

出于这个问题的目的，我们假设可想象的最糟糕的意大利面条代码隐藏在$user或Task中的global-scope中.

For the purposes of this question let's assume the worst spaghetti code imaginable is hiding in global-scope somewhere in $user or Task.

哪些工具，PHP技巧或调试伏都教可以帮助我发现并解决问题?

推荐答案

PHP没有垃圾收集器.它使用引用计数来管理内存.因此，内存泄漏的最常见来源是循环引用和全局变量.恐怕，如果使用框架，您将需要大量代码来查找它.最简单的工具是有选择地对memory_get_usage进行调用，并将其范围缩小到代码泄漏的位置.您还可以使用 xdebug 创建代码跟踪.使用执行跟踪和show_mem_delta.

PHP doesn't have a garbage collector. It uses reference counting to manage memory. Thus, the most common source of memory leaks are cyclic references and global variables. If you use a framework, you'll have a lot of code to trawl through to find it, I'm afraid. The simplest instrument is to selectively place calls to memory_get_usage and narrow it down to where the code leaks. You can also use xdebug to create a trace of the code. Run the code with execution traces and show_mem_delta.

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