PHP error category
Sessions & Cookies
Session persistence and cookies.
Sessions & Cookies errors arise when session persistence and cookies affect an executing PHP application or its supporting service. Use the exact signature and runtime context to narrow the cause before changing configuration.
The guides in this category separate code defects from environment differences, show focused diagnostics, and favor site-scoped corrections that preserve unrelated applications.
Guides in this category
| Title | Pattern | Severity |
|---|---|---|
| Cannot modify header information — headers already sent | Warning: Cannot modify header information - headers already sent by (output started at %s:%d) in %s on line %d |
warning |
| Cannot send session cache limiter or cookie | Warning: session_start(): Cannot send session %s - headers already sent |
warning |
| SameSite blocks PHP session cookie | Cookie "%s" was rejected because it had the "SameSite=%s" attribute |
warning |
| Secure session cookie missing over HTTP | Set-Cookie: %s; Secure |
warning |
| session_start called while a session is active | Notice: session_start(): Ignoring session_start() because a session is already active |
notice |
| session_start cannot run after output | Warning: session_start(): Session cannot be started after headers have already been sent |
warning |
| session_start open failed | Warning: session_start(): open(/var/lib/php/sessions/sess_abc, O_RDWR) failed: Permission denied |
warning |