How Long Does My PHP Session Actually Last?

Assessing Session Duration from Technical Data

Many developers encounter uncertainty when determining the lifespan of their PHP sessions based on technical configurations. Here's a detailed analysis to help you understand how your session duration is determined.

The configuration setting "session.gc_maxlifetime" specifies the maximum time since the last change in session data, not the last use of session_start(). However, PHP's session handling involves a garbage collector that introduces complexity.

The garbage collector is invoked with a probability determined by "session.gc_probability" and "session.gc_divisor." By default, these values are 1 and 100, meaning the collector is triggered in only 1% of session_start() calls. This can lead to extended session usage beyond the theoretical timeout specified by "session.gc_maxlifetime."

Given this behavior, it's advisable to implement a custom session timeout mechanism for greater control over duration. This approach provides a reliable way to manage user sessions and prevent prolonged usage after actual expiration.

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