php - Memcached::touchByKey(): touch is only supported with binary protocol -

i'm trying use touchbykey memcached function warning pops up:

memcached::touchbykey(): touch supported binary protocol

i found use like:$mc->setoption(\memcached::opt_binary_protocol, true); on client side.

the same problem happens touch()

my question is, need change on memcache server itself? why requiring binary protocol? why isn't functionality available current ascii protocol?

when implementation done done binary protocol , there no specific reason why can't done ascii protocol. implementer didn't want spend time both. thing want note binary protocol faster ascii protocol. unless have specific reason using ascii recommend switching binary. if submit patch memcached support ascii protocol i'm sure merged project owners.