Responses:

x clear

• php default (files in temporary directory), uses flock
• custom handler, files, no locking
• custom handler, files, per session locking using flock
• custom handler, mysql, one row per session, no locking
• custom handler, mysql, one row per session, with a mysql advisory lock per session
• custom handler, mysql, one row per variable, no locking
• custom handler, mysql, one row per variable, with a mysql advisory lock per variable