Warning: session_start(): Failed to read session data: files (path: /var/lib/php/sessions)
ID: php/session-expired
Version Compatibility
| Version | Status | Introduced | Deprecated | Notes |
|---|---|---|---|---|
| 83 | active | — | — | — |
Root Cause
PHP session errors occur when the session handler cannot read or write session data. Common causes include incorrect session.save_path permissions, the session directory not existing, session garbage collection deleting active sessions prematurely, or misconfigured session handlers (Redis/Memcached) failing silently.
genericWorkarounds
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89% success Verify session.save_path exists with correct permissions and use a persistent session handler
Check session.save_path with 'php -r "echo ini_get(\"session.save_path\");"'. Ensure the directory exists and is writable by the PHP process: 'mkdir -p /var/lib/php/sessions && chown www-data:www-data /var/lib/php/sessions && chmod 700 /var/lib/php/sessions'. For multi-server setups, switch to Redis or database session handler.
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87% success Configure proper session garbage collection and use Redis for high-traffic applications
Set session.gc_maxlifetime to match your desired session duration (e.g., 1440 for 24 minutes). Set session.gc_probability/session.gc_divisor appropriately (e.g., 1/100). For production, use Redis: set session.save_handler=redis and session.save_path='tcp://127.0.0.1:6379' in php.ini.
Dead Ends
Common approaches that don't work:
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Setting session.gc_maxlifetime to an extremely high value to prevent cleanup
70% fail
Setting a very high gc_maxlifetime causes session files to accumulate on disk indefinitely. On high-traffic sites this can fill the disk partition, cause inode exhaustion, and make the session directory extremely slow to scan. It also keeps stale sessions around as a security risk.
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Storing session data in cookies using client-side sessions
72% fail
Storing all session data in cookies exposes it to the client, has a 4KB size limit, increases every HTTP request size, and can be tampered with unless encrypted and signed. Sensitive data like user roles or permissions should never be stored in cookies.