PHP Session Side-Effect Warning: Trouble with Global Variables

When attempting to host a PHP website, you may encounter a warning stating that your script relies on a session side-effect that was deprecated in PHP 4.2.3. This warning arises when the session extension does not recognize global variables as a data source unless the register_globals option is enabled.

Understanding the Issue

Global variables are variables that can be accessed from any scope within the script. In older versions of PHP, the session extension would automatically register global variables into the session. However, this behavior was considered a security risk and was removed in PHP 4.2.3.

Tracking Down the Source

To identify the source of the warning, look for instances where you are using global variables in your session context. Specifically, check for variables with the same name as session variables, as this can cause the warning.

Disabling the Warning

You can disable the warning by setting the PHP configuration options 'session.bug_compat_warn' and 'session.bug_compat_42' to 'off'. These settings can be configured in the following ways:

• php.ini:

session.bug_compat_warn = 0
session.bug_compat_42 = 0

• .htaccess:

php_value session.bug_compat_warn 0
php_value session.bug_compat_42 0

Alternate Solution:

Alternatively, you can prevent PHP from attempting to find existing variables by adding the following lines to your script:

ini_set('session.bug_compat_warn', 0);
ini_set('session.bug_compat_42', 0);