(PECL yac >= 1.0.0)
Yac::__construct — Constructor
prefix is used to prepended to keys, this could be used to avoiding conflicts between apps.
prefixstring prefix
   Throws an Exception if Yac is not enabled. Throws 
   Exception if prefix exceeds 
   max key length of 48 (YAC_MAX_KEY_LEN) bytes.
  
