PHP garbage collection and memory leaks

25 Feb

tags: garbage collection, memory leak, php

Hello there! If you are new here, you might want to subscribe to the RSS feed if you find this post interesting.

Been working on a command line script that takes days to finish execution (yes, DAYS). Unfortunately, it had a healthy flow of memory leaking. It would fatally crash with your typical "out of memory" error.

I spent hours debugging the potential source - free'd results of mysql queries, unset variables, you name it I tried it. I kind of gave up and instead chose to add in a "start at" parameter so that I could just re-execute and jump back in to the loop where it crashed last time.

Today, through natural processes of improving functionality and cleaning code, I moved the block of code that was leaking memory into a function so that it could be recycled elsewhere. By simply moving the code into a function I suspect PHP now garbage collects after each call and memory no longer hemorrhages from its veins.

I hope this helps someone else out there!

If you liked this post, consider subscribing to our RSS feed!

Paul

This helped... I'm working with objects, so it's a little different for me.

You need to cache objects that are created within a method, where the method's return value is the result of a function call on the newly created object.


class a {

  function b() { 

    $c = new c();

    // memory leaking here.

    return $c->d();

  }

}

class c { 

  function d() { 

    return 3+5;

  }

}



Fixed:

class a {

  var $objc;

  function b() { 

    // create if not exists, else use cached object.

    if( !is_object($this->objc) ) { 

      $this->objc = new c();

    }

    return $this->objc->d();

  }

}

Brandon Savage

This did help me. Thanks for posting it. I did exactly what you did and my application works properly.
Tom Lancaster

thanks for this insight. You've just saved me a lot of time on a script that I'm using to update my whole database. This technique works.

blog comments powered by Disqus

Subscribe in a reader

PHP garbage collection and memory leaks

Recent Posts

Categories

Archives

Recent Entries

Recent Comments

Most Commented