On his blog today, Alex Netkachov has posted a suggestion of how to combat a common issue facing PHP scripts - their memory usage.
PHP has a build-in garbage collector so you do not need to track the links on the objects, allocate memory for objects and delete them when they are not longer necessary. Things seem so perfect that developers do not even know that their scripts allocate a lot of memory until their server stops processing requests because of the out of memory error.
His example is the processing of a parent/child relationship tree. If not managed correctly, the variables being used could get out of hand quite quickly. Alex recommends the use of a "destructor" at the end of each iteration to help destroy variables and values no longer needed.