session_register()

(PHP 4, PHP 5 < 5.4.0)

在当前会话中注册一个或多个全局变量

说明

session_register(mixed $name[,mixed$...]): bool

session_register()accepts a variable number of arguments, any of which can be either a string holding the name of a variable or an array consisting of variable names or other arrays. For each name,session_register()registers the global variable with that name in the current session.

You can also create a session variable by simply setting the appropriate member of the$_SESSIONarray.

<?php
// Use of session_register() is deprecated
$barney = "A big purple dinosaur.";
session_register("barney");
// Use of $_SESSION is preferred
$_SESSION["zim"] = "An invader from another planet.";
?>

Ifsession_start()was not called before this function is called, an implicit call tosession_start()with no parameters will be made.$_SESSIONdoes not mimic this behavior and requiressession_start()before use.

Warning
本函数已自 PHP 5.3.0 起废弃并将自PHP 5.4.0 起移除。

参数

$name: A string holding the name of a variable or an array consisting of variable names or other arrays.
...

返回值

成功时返回TRUE，或者在失败时返回FALSE。

注释

Caution

If you want your script to work regardless ofregister_globals, you need to instead use the$_SESSIONarray as$_SESSIONentries are automatically registered. If your script usessession_register(), it will not work in environments where the PHP directiveregister_globalsis disabled.

Note:register_globals 重要说明：
自 PHP 4.2.0 起，PHP 指令register_globals的默认值为off。PHP 社区鼓励开发者不要依赖于此指令，用其他手段替代，例如superglobals。

Caution

This registers aglobalvariable. If you want to register a session variable from within a function, you need to make sure to make it global using theglobalkeyword or the$GLOBALS[]array, or use the special session arrays as noted below.

Caution

If you are using$_SESSION, do not usesession_register(),session_is_registered(),andsession_unregister().

Note:
It is currently impossible to register resource variables in a session. For example, you cannot create a connection to a database and store the connection id as a session variable and expect the connection to still be valid the next time the session is restored. PHP functions that return a resource are identified by having a return type ofresourcein their function definition. A list of functions that return resources are available in theresource typesappendix.
If$_SESSIONis used, assign values to$_SESSION. For example:$_SESSION['var']='ABC';

参见

session_is_registered()检查变量是否在会话中已经注册
session_unregister()Unregister a global variable from the current session
$_SESSION

Below is a fix that may be included in older code to make it work with PHP6. 
When needed it recreates the functions
- session_register()
- session_is_registered()
- session_unregister()
The functions inside the function fix_session_register() are only available after fix_session_register() has run.
Therefore in PHP<6 where there already is a session_register() nothing happens.
<?php
// Fix for removed Session functions
function fix_session_register(){
  function session_register(){
    $args = func_get_args();
    foreach ($args as $key){
      $_SESSION[$key]=$GLOBALS[$key];
    }
  }
  function session_is_registered($key){
    return isset($_SESSION[$key]);
  }
  function session_unregister($key){
    unset($_SESSION[$key]);
  }
}
if (!function_exists('session_register')) fix_session_register();
?>
[EDIT BY danbrown AT php DOT net: Bugfix provided by "dr3w" on 02-APR-2010: "its [sic] function_exists with an S at the end".]

if you remove session_register() calls and replace with $_SESSION assignments, make sure that it wasn't being used in place of session_start(). If it was, you'll need to add a call to session_start() too, before you assign to $_SESSION.

Something that hasn't really been touch on when migrating old code, is that changes to variables made AFTER the session_register() call are still included in the session state.
A lot of the implementations above only add the entry to $_SESSION[] at the point it's called.
If the old code relies on this behaviour, you will either need to have code called on exit to assign back to $_SESSION, or replace it in entirety with $_SESSION usage. With over 1000 uses of the session_ functions, this is a bit daunting!

There are a few compat functions for session_register here that had me tripped up. 
1) when registering a session var, the value of the global you are registering should *not* override an existing session value. that would defeat the purpose of the session. instead the global should be refered to the sessions value.
2) the global should become a reference to the sessions value, so that when you change the globals value later, the session variable should change too.
This is what I'm using now
<?php
if (!function_exists('session_register')) {
   function session_register($name){
    global $$name;
    if (!isset($_SESSION[$name])) {
      $_SESSION[$name] = $$name;
     } 
     $$name = &$_SESSION[$name]; 
   }
  }
?>

This code replaces the removed function "session_register" for PHP >= 5.4.0 
"session_start()" must be called before.
<?php
function session_register($name){
  if(isset($GLOBALS[$name])) $_SESSION[$name] = $GLOBALS[$name];
  $GLOBALS[$name] = &$_SESSION[$name];
}
?>

If you want to store an object into the session, you have to check up that object can be serialized at all. 
For example, if your object contains aggregated PDO object (which can't be serialized), you will get an error and no data would be stored.

If you have an old code with a lot of call to the function session_register(), and you would like to make it compatible with PHP5 or PHP6, instead of rewriting all your code by replacing this function by $_SESSION['var']="val"; you could use the function set_session_vars(), that is used exactly the same way than session_register() (but there is no implicit call to session_start() ).
<?php
function set_session_vars() {
  $nb_args=func_num_args();
  $arg_list=func_get_args();
  for($i=0;$i<$nb_args;$i++) {
    global $$arg_list[$i];
    $_SESSION[$arg_list[$i]] = $$arg_list[$i];
  }
}
?>

I've noticed that if you try to assign a value to a session variable with a numeric name, the variable will not exist in future sessions.
For example, if you do something like:
session_start();
$_SESSION['14'] = "blah";
print_r($_SESSION);
It'll display:
Array ( [14] => "blah" )
But if on another page (with same session) you try
session_start();
print_r($_SESSION);
$_SESSION[14] will no longer exist.
Maybe everyone else already knows this, but I didn't realize it until messing around with a broken script for quite a while.

You *MUST* notice that
session_register($var)
*IS NOT* 
$_SESSION[$var] = $$var;
it is 
if (!isset($_SESSION[$var]))
 $_SESSION[$var] = $$var;
when migrating from old style code.

If you have many websites with these functions in the source code (like me) you can include the following functions in some kind of include.php that you have:
function session_register($session)
{
 //
}
function session_unregister($session)
{
 unset($_SESSION[$session]);
}
In this way the PHP interpreter detects the functions and do not return the error, and the maintenance work is minimized.

If you are using sessions and use session_register() to register objects, these objects are serialized automatically at the end of each PHP page, and are unserialized automatically on each of the following pages. This basically means that these objects can show up on any of your pages once they become part of your session.

in addition to function set_session_vars instead of replacing all $var with $_SESSION['var'],
 you could get all set session-vars in prevoius scripts with this function
<?php
function get_session_vars() {
  $nb_args=func_num_args();
  $arg_list=func_get_args();
  for($i=0;$i<$nb_args;$i++) {
    global $$arg_list[$i] = $_SESSION[$arg_list[$i]];
  }
}
?>

Please note that if you use a "|" sign in a variable name your entire session will be cleared, so the example below will clear out all the contents of your session. 
<?php
session_start();
$_SESSION["foo|bar"] = "foo";
?>
It took me quite some time finding out why my session data kept disappearing. According to this bugreport this behaviour is intended.
http://bugs.php.net/bug.php?id=33786

Make sure you put session_start() at the beggining of your script.
My sessions kept unsetting and I finally figured out why.
On my script, session_start() has to be said and uses cookies to set the session. 
But I was outputting html prior to calling session_start(), which prevented it from succeeding becouse it uses the header function to place the cookies.
Once html has been outputed, session_start() can't use the header function to set cookies, hence session_start() fails and no session can be started.

For those of you who use this function (session_register that is), even though the manual does specify that this function implicitly calls session_start(), I just wanted to reiterate that fact. It is also important to know that if you ever switch from session_register to using $_SESSION, make sure to call session_start before adding items to the $_SESSION variable, because unlike session_register, no implicit call to session_start is done.
Another reason I explain this is because I ran into a problem in which you can add items to the $_SESSION variable all you want, but if session_start is not called before adding them, they will not actually be saved to the session. Using the same code, though, and replacing the $_SESSION assignments with session_register without calling session_start WILL save that info to the session.
It would be nice to have PHP check for writes to the $_SESSION variable and complain with a warning if session_start hasn't been called.