Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

SID (string)
Constant containing either the session name and session ID in the form of "name=ID" or empty string if session ID was set in an appropriate session cookie. This is the same id as the one returned by session_id().
PHP_SESSION_DISABLED (int)
Since PHP 5.4.0. Return value of session_status() if sessions are disabled.
PHP_SESSION_NONE (int)
Since PHP 5.4.0. Return value of session_status() if sessions are enabled, but no session exists.
PHP_SESSION_ACTIVE (int)
Since PHP 5.4.0. Return value of session_status() if sessions are enabled, and a session exists.
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User Contributed Notes 2 notes

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12
sarath dot jasrin at gmail dot com
3 years ago
Check whether session started using Predefined Constants

if (session_status() == PHP_SESSION_NONE) {
    session_start();
}
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9
Anonymous
3 years ago
SID constant defined dynamically!

var_dump(defined('SID'));  // bool(false) - Not defined...
session_start();
var_dump(defined('SID'));  // bool(true) - Defined now!
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