Description
bool 
memcache_debug ( int on_off )
   memcache_debug() turns on debug output if parameter
   on_off is equal to 1 and turns off if it's 0.
  
注: 
    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.