Description
bool 
ibase_rollback_ret ( [resource link_identifier])
     If called without an argument, this function rolls back the default transaction 
     of the default link. If the argument is a connection identifier, the default 
     transaction of the corresponding connection will be rolled back. If the argument
     is a transaction identifier, the corresponding transaction will be rolled back.
     The transaction context will be retained, so statements executed from within
     this transaction will not be invalidated.
     如果成功则返回 TRUE,失败则返回 FALSE。