Top 10 most expensive operations 

These are the most expensive operations in this test (by time)

1. file_put_contents()
2. opendir() readdir() closedir()
3. scandir()
4. fopen() fread() fclose()
5. memcache->get()
6. memcache->set()
7. implode('\n', file())
8. include()
9. include_once()
10. file_get_contents()

These are the biggest time savers (per call)

1. xcache_set() vs. file_put_contents()
2. xcache_get() vs. memcache->get()
3. xcache_set() vs. memcache->set()
4. file_get_contents() vs. fopen(), fread(), fclose()
5. file_get_contents() vs. implode('\n', file())
6. include(relative) vs. include(full_path)
7. require_once() vs. include()
8. scandir() vs. opendir() readdir() closedir()
9. static method vs. call_user_func()
10. preg_match(/regex/i) vs. eregi(regex)