![]() Most of the code is extracted from our tideways extension and enhanced by a simple CLI mode to print statistics without requiring changes to your code. It is based on the garbage collection hook that I co-proposed with Adam Harvey for PHP 7 and up. This is where our small PHP extension garbage_stats comes to the rescue. ![]() The optimal performance strategy is to enable the garbage collector when the GC can clean up as many possible (high efficiency, many cleanups) from the potential 10000 cyclic references and to disable it when it finds out that most of them are still used (low efficiency, few cleanups).īut how then can you find out if you need to enable or disable the garbage collection or not? As I mentioned PHP does not actually provide statistics about cleanup mechanisms 2 and 3. ![]() If you call the function gc_collect_cycles(), then collection of cyclic references is triggered explicitly even if you don’t have 10000 of them in memory yet. The collector is enabled by default in every request, but it can be toggled with the functions gc_enable() and gc_disable(). It is triggered whenever 10000 possible cyclic objects or arrays are currently in memory and one of them falls out of scope. If a variable is part of a cyclic reference, where A points to B and B back to A, then the variable can only be cleaned up by PHPs cycle garbage collector. You can force this early by using unset() to end variables scope early. If a variable falls out of scope and is not used in any other place of the currently executed code anymore, then it is garbage collected automatically. Please see Anthony Ferrara’s post on “ What about garbage” if you want to dive deep into this topic. The following summary is as bare bones as it can get to understand PHP memory. Because sometimes you need to enable the garbage collector and sometimes its better to disable it. Yeah, no thank you!īefore I show you a tool to access all the necessary information, you should first understand the available optimization potential and trade-offs with PHPs GC. Sadly, answers to these questions are not available to you from the PHP engine, unless you want to recompile with obscure debug flags. Maybe you fear that your application is suffering from a similar inefficient garbage collection usage than Composer did three years ago, where selectively disabling the collector improved their performance by up to 90%. However, arbitrarily littering your code with gc_enable(), gc_disable() and gc_collect_cycles() calls everywhere does not automatically help and obviously reduces the expressiveness of your code.ĭo you know if the garbage collector is slowing down your requests or speeding them up? When does it get triggered automatically? How much memory does each run clean up? Is your script running out of memory and you are looking for ways to reduce it? PHP’s GC is a way to to reduce the memory of your script. The behaviour of PHP’s Garbage Collection (GC) can be a small mystery and you might wonder how it works and if you can optimize its usage for your application. How to optimize the PHP garbage collector usage to improve memory and performance?
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