PHP Session Side-Effect Warning with Global Variables as a Source of Data

PHP session side-effect warning with global variables as a source of data

basically you have a variable with the same name as your session. ex:

$_SESSION['var1'] = null;
$var1 = 'something';

which will reproduce this error. you can stop PHP from trying to find existing variables and warning you about them by adding these lines to your script:

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

these values can be set in php.ini or .htaccess as well

Warning: Unknown: Your script possibly relies on a session side-effect which existed until PHP 4.2.3

There is a session variable given the same name as some existing global variable (i.e. both $_SESSION['name'] and $name exists).

Rename either of them.

It should be a quite duplicate question, as it just occurred to me.

PHP session side-effect warning - how to get solve?

It is happening because of

session_register("username");  

It is not recommended, and deprecated as of PHP 5.3.

If you want your script to work regardless of register_globals, you need to instead use the $_SESSION array as $_SESSION entries are automatically registered. If your script uses session_register(), it will not work in environments where the PHP directive register_globals is disabled.

Source.

As we all know, register_globals is terrible, and should always be off.

The most common way to register a session var is with the $_SESSION superglobal, i.e.

$_SESSION['username'] = $username;

PHP session side-effect warning with global variables as a source of data

basically you have a variable with the same name as your session. ex:

$_SESSION['var1'] = null;
$var1 = 'something';

which will reproduce this error. you can stop PHP from trying to find existing variables and warning you about them by adding these lines to your script:

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

these values can be set in php.ini or .htaccess as well

PHP Session warning issue

This means you have a variable with the same name as your session variable is as below.

$_SESSION['variable'] = null;
$variable = 'data';

You can stop PHP from trying to find existing variables and warning you about them by adding these lines to your script in php.ini or .htaccess

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

PHP declaring global and session variables

Try setting session.bug_compat_42 to off, it will turn off the functionality the warning is about. c.f. http://php.net/manual/en/session.configuration.php

PHP session extension does not consider global variables

Hi, I had the same problem, and in my
case it was here $arrFormData and here
$_SESSION['arrFormData'] The thing is
having the same variable name. In my
case it happened on a $_GET array,
but I guess it should be similar. Give
it a try on renaming the $arrFormData
variable to something else and let us
know if it worked.

Source.

It is because somewhere you have the same variable name as the key of your $_SESSION global.

Example

session_start();
$_SESSION['a'] = 1;
$a = 1;

You can disable the error by turning session.bug_compat_42 off in your php.ini or using ini_set().

How can I avoid PHP session errors?

If your variable names are the same as the session parameters then this version of PHP will incorrectly recognize this as the programmer incorrectly relying on register_globals for session variables. Rename your variables and the warning should go away.

$mySessionVar = $_session["sessionVar"]; 

and not

$sessionVar = $_session["sessionVar"]; 

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