First I have read the documentation both on this site and at ZEND.<br>
The test case was taken from the artical "PHP4 Customer Session <br>
Handler Test Script" by Ying Zhang (ying@zippydesign.com) at the<br>
HTTP://www.phpbuilder.com site.<br>
<br>
This is a complex issue.  It would be reasonable to expect PHP4 to<br>
behave according to what is set in PHP.ini as a default....  <br>
The following are my results using PHP4.0.1pl2.<br>
<br>
1) With 'session.save_handler' not defined (commented out):<br>
<br>
    The online documentation for the session_module_name states that <br>
    the 'module' can be set in the call:<br>
          "session_module_name() returns the name of the current <br>
           session module. If module is specified, that module <br>
           will be used instead."<br>
           <br>
    Any attempt to do so results in an error regardless of whether<br>
    or not any handler has been defined by the user:<br>
        Fatal error: Failed to initialize session module in <br>
        .../handler/test.php on line 38   <br>
        This occurs at the session_start() call.<br>
    <br>
    Not setting a 'module' will return the current handler.  With<br>
    nothing defined in PHP.ini, a value of 'files' is returned.<br>
    <br>
    If you define your 'user' handlers and call 'session_set_save_handler'<br>
    before the 'session_module_name' call, a value of user is returned.<br>
    However, any variables registered in this session Do Not maintain<br>
    their value.  It is like the handlers are accepted, but are not used.<br>
    <br>
    Thus, not having 'session.save_handler' defined in PHP.ini does not<br>
    help.  However, the 'files' modules does work (e.g. no defined user<br>
    handlers) in this situation.<br>
    <br>
2)  If we define 'session.save_handler' in PHP.ini with a value of 'files',<br>
    then the same results as above occur.<br>
    <br>
    Thus in this case, we have explicitly defined the handler as file and<br>
    the only thing that works is the 'files' module.<br>
    <br>
3)  If we define the 'session.save_handler' in PHP.ini with a value of<br>
    'user', then things change to the opposite.  You must define an <br>
    user handler.  If you do not, registered variables are not retained.<br>
    <br>
    Thus the 'user' module dos work in this case and the variables are<br>
    passed from invocation to invocation.<br>
    <br>
This leaves us with the following:<br>
    a.  One handler method can be defined at a time.  And only one.<br>
    b.  There is a very tight coupling between the PHP.ini file and<br>
        what can be done by the programmer.<br>
        <br>
Conclusions.  You can get a 'user' handler defined to track the session<br>
data in a database.  But, it must be only one way for all applications.<br>
(It could be different databases for different applications however.)<br>
It would seem that this is wrong.  It should be reasonable to define one<br>
behavior for one application and another for others.<br>
<br>
I hope this has help to clear up a few questions.