Database Session Handling and Garbage Collector
Note for self: When using a distributed session storage with symfony (sfMySQLSessionStorage, sfMemcacheSessionStorage, sfPDOSessionStorage, etc.), don’t forget to check that session.gc_probability must not be set to 0 in the php.ini, and that the line is not commented, which seems to be the case on some PHP distributions.
; Define the probability that the 'garbage collection' process is started
; on every session initialization.
; The probability is calculated by using gc_probability/gc_divisor,
; e.g. 1/100 means there is a 1% chance that the GC process starts
; on each request.
session.gc_probability = 1
session.gc_divisor = 100
If set to 0, the session garbage collector will never run, and sessions will pile up forever in your storage facility - eventually inflating the storage space way too much for decent performance.