CODEWITHSUNDEEP
phpmemory-management
Doo Dah
Doo Dah

Reputation: 4029

PHP Memory management and arrays

Do I need to worry about memory leaks with PHP? In particular, I have the following code that is being called from a browser. When the call finishes, is everything cleaned up properly, or, do I need to clear the memory created by the first array that was created?

class SomeClass
{
  var $someArray = array();

  function someMethod()
  {
     $this->someArray[1] = "Some Value 1";
     $this->someArray[2] = "Some Value 2";
     $this->someArray[3] = "Some Value 3";
     $this->someArray = array();
     $this->someArray[1] = "Some other Value";
     $this->someArray[2] = "Some other Value";
     $this->someArray[3] = "Some other Value";
  }
}

someMethod();

Thanks, Scott

Upvotes: 1

Views: 724

Answers (3)

Emil Vikström
Emil Vikström

Reputation: 91983

There actually do exist memory problems if you run mod_php through Apache with the mpm_prefork behavior. The problem is that memory consumed by PHP is not released back to the operating system. The same Apache process can reuse the memory for subsequent requests, but it can't be used by other programs (not even other Apache processes).

One solution is to restart the processes from time to time, for example by setting the MaxRequestsPerChild setting to something rather low (100 or so, maybe lower for lightly loaded servers). The best solution is to not use mod_php at all but instead run PHP through FastCGI.

This is a sysadmin issue though, not a programmer issue.

Upvotes: 1

alex
alex

Reputation: 490637

Do I need to worry about memory leaks with PHP?

It's possible to have a cyclic reference in PHP where the refcount of the zval never drops to 0. This will cause a memory leak (GC won't clean up objects that have a reference to them). This has been fixed in >= PHP 5.3.

In particular, I have the following code that is being called from a browser. When the call finishes, is everything cleaned up properly, or, do I need to clear the memory created by the first array that was created?

PHP scripts have a request lifecycle (run application, return response, close application), so it shouldn't be a worry. All memory used by your application should be marked as free'd when your application finishes, ready to be overwritten on the next request.

Upvotes: 3

Corbin
Corbin

Reputation: 33467

If you're super paranoid, you can always unset things, however, PHP is a garbage collected language meaning that unless there is a bug in the core or in an extension, there is never going to be a memory leak.

More information

On a side note, you should use the newer PHP 5 OOP syntax. And, someMethod would be an error. It would need to be $obj->someMethod() where $obj is an instance of the class.

Upvotes: 1

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