I've never done my own garbage collection, and PHP just updated it in 5.3.
PHP works, it's fast as heck, and I can do anything you can do in python/perl just as well and way faster.
I don't know about python/perl but there are operations in PHP that need 200MB of memory which I could achieve in C with only 20KB of memory.
That's a 10,000x increase in memory consumption for PHP. If this has improved in version 5.5 I can't wait to give it a try.
And it's not just memory consumption, there are times when I run a xhprof on some slow PHP code and find out it's spending 90% of it's time allocating and/or freeing memory. If it used less memory, it would spend less time managing it.
PHP is a great language, but it's definitely not perfect. Memory and performance are "good enough" in most cases, but it's far from great.
Also, I have had to do my own manual garbage collection at times. There are no manual malloc/free API calls but I definitely do need to make use of unset() at times or otherwise refactor my code to reduce memory consumption.