memcache_debug() turns on debug output if parameter
on_off is equal to TRUE and turns off if it's
memcache_debug() is accessible only if PHP was built
with --enable-debug option and always returns TRUE in this case.
Otherwise, this function has no effect and always returns FALSE.
Turns debug output on if equals to TRUE.
Turns debug output off if equals to FALSE.
Returns TRUE if PHP was built with --enable-debug option, otherwise