XCache is a PHP opcode cacher. This is good and well as it speeds up pageloads by removing PHP parsing overhead. On the downside, you must remember to restart your PHP processes after changing PHP files, as XCache doesn’t seem to perform stat()s on the files to check if they’ve been updated.
The whole modern world has divided itself into Conservatives and Progressives. The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected.— G.K. Chesterton