Derick Rethans' Blog: Collecting Garbage: Cleaning Up
In this second part of the three part column on the new garbage collecting mechanism in PHP 5.3, we'll dive into a solution to the problem with circular references. If we look quickly back, we found that by using code like the [first example], an in-request memory leak is created.
He goes on to briefly describe the synchronous algorithm (including a few more helpful graphs to show the flow) and how that has worked its way into the PHP garbage collection methods. He also points out that this collection can be turned off and on via the gc_enable and gc_disable functions. Keep an eye out for the next part of the series where he gets into more detail on how this is all integrated into PHP.