I believe mod_perl had the 'benefit' of persistent/shared state, which meant multiple users might conflict with each other (via shared memory, IIRC), and the mo

I believe mod_perl had the 'benefit' of persistent/shared state, which meant multiple users might conflict with each other (via shared memory, IIRC), and the mod_php - while it kept an interpreter bundled in each apache process - didn't leave anything around after a request.