A warning for PHPSession

Warning Full Text: PHPWarning: Unknown: Yourscriptpossiblyreliesonasessionside-effectwhichexisteduntilPHP4.2.3.Pleasebeadvisedthatthesessionextensi

The warning is as follows:

PHP Warning: Unknown: Your script possibly relies on a session side-effect

Which existed until PHP 4.2.3. Please be advised that the session extension does

Not consider global variables as a source of data, unless register_globals is enabled.

You can disable this functionality and this warning by setting session. bug_compat_42

Or session. bug_compat_warn to off, respectively. in Unknown on

There are many ways to solve this problem on the Internet, but I don't know the answer. what is the real reason? how can this problem be solved?

Remember this first. at PHP4.2, register_globals is set to OFF by default.

After 4.2.3, to be compatible with the previous mode, PHP introduced bug_compat_42. when this option is enabled (enabled by default), PHP will allow automatic use of the variables in the SESSION as global variables. however, if the bug_compat_warn option is enabled, this feature is reported to be used.

Let's look at a piece of code,

Session_start ();

Var_dump ($ _ SESSION );

$ Name = 'laruence ';

$ _ SESSION ['name'] = null;

?>

The above code, when bug_compat_42 is enabled and register_globals is disabled, refreshes the page output for the following two times:

// First time:

Array (0 ){}

// Second time

Array (1) {["a"] => string (8) "laruence "}

Why is the second time not NULL? because when bug_compat_42 is enabled, PHP considers the variable a as a reference of $ _ SESSION ['A']. when session_close, write back the value of variable.

In this process, if bug_compat_warn is enabled, a warning at the beginning of the article will be thrown.

So, that it is ~

So what conditions does it provide a warning? With these conditions, we can avoid this warning,

In PHPSRC/ext/session. c, there are all the answers we want:

Static void php_session_save_current_state (TSRMLS_D )/*{{{*/

{

Int ret = FAILURE;

IF_SESSION_VARS (){

// If a Session array exists

If (PS (bug_compat )&&! PG (register_globals )){

HashTable * ht = Z_ARRVAL_P (PS (http_session_vars ));

HashPosition pos;

Zval ** val;

Int do_warn = 0;

Zend_hash_internal_pointer_reset_ex (ht, & pos );

While (zend_hash_get_current_data_ex (ht

, (Void **) & val, & pos )! = FAILURE ){

If (Z_TYPE_PP (val) = IS_NULL) {// The variable is null.

If (migrate_global (ht, & pos TSRMLS_CC) {// variable write-back

Do_warn = 1;

}

}

Zend_hash_move_forward_ex (ht, & pos );

}

If (do_warn & PS (bug_compat_warn )){

Php_error_docref (NULL TSRMLS_CC, E_WARNING, "Your script possibly

Relies on a session side-effect which existed until PHP 4.2.3 ..........");

// Omitted later

It can be seen that if you do not enable bug_compat_42 (this feature is rarely used now, it may be confusing if you do not enable it), or if you do not start bug_compat_warn, or when register_globals is enabled, you will not see this warning.

In addition, if you enable bug_compat_42, you may encounter the following NOTICE ..

PHP Notice: Unknown: The session bug compatibility code will not try

Locate the global variable $324324 due to its numeric nature in Unknown on line 0

This is a warning when you use a digital index in $ _ SESSION.