The Ghost in the Opcode: A Practical Guide to Tuning APC, APCu, and PHP Caches Without Losing Your Sanity
APC is dead, APCu lives, and OPcache is doing the actual heavy lifting — but the tuning instincts behind "alternate PHP cache" never went away. Here's how to read the invisible layer between your code and your users, tune it properly, and stop guessing at config values.