Couch Sessions - But There's More Than One Way To Skin A Cat... (
Page 4 of 4 )
Of
course, if your Web server is still running PHP3, you're not going to be able to
use any of the code provided thus far. But don't despair - there does exist an
alternate solution for PHP3 users. It's called PHPLIB, and it provides a number
of useful PHP classes that allow you to add session management capabilities to
PHP3. Installation instructions are available in the package, and you'll also
need to modify the "local.inc" configuration file to create your own
classes.
As in PHP4, you need to call a predefined page_open() function
each time you initiate a session. PHPLIB comes with a default session class
named Example_Session - you can modify this by changing the values in the
"local.inc" file - which is what we've used in the following example:
<?php
page_open(array("sess" => "Example_Session"));
?>
It's important that the page_open() call happen before any
output is sent to the browser. And in order to register your session variables,
the following statement will do the job.
<?php
// initiate a session
page_open(array("sess" => "Example_Session"));
// register a variable for the session.
$sess->register('username');
?>
Each page must also have a corresponding page_close()
function, which is used to make sure that all changes are saved to the database.
<?php
page_close();
?>
Other than this, most of your code stays the same. Take a
look at this PHPLIB version of the previous example:
<?php
//initiate a session
page_open(array("sess" => "Custom_Session"));
// register the session variables - note the syntax
$sess->register('username');
$sess->register('stock1');
$sess->register('stock2');
$sess->register('stock3');
$sess->register('stock4');
// connect to MySQL
$db = mysql_connect("someserver.com", "tom", "jones");
// select database on MySQL server
mysql_select_db("stock_db",$db);
// query database using SQL
$query = "select stock_pref1,stock_pref2,stock_pref3,stock_pref4 from
user_info where username='$username'";
$result = mysql_query($query,$db);
// get stock symbols from database
// and assign to session variables
list($stock1,$stock2,$stock3,$stock4) = mysql_fetch_row($result);
// output
echo "Hi $username!<br>";
echo "Your selected stocks are:<br>";
echo "$stock1<br>";
echo "$stock2<br>";
echo "$stock3<br>";
echo "$stock4<br>";
// code to generate rest of page
// save data back to database
page_close();
?>
As you can see, once you've got the hang of the PHP4 version,
it's not too difficult to understand the PHPLIB version - not at all strange
when you consider that the native session support in PHP4 is heavily based on
the PHPLIB model. And if you're interested, PHPLIB actually takes session
management much further with its authentication and permission classes, which
allow you to grant or deny access to users based on permissions in a database -
take a look at the documentation for examples on how to use these
features.
PHPLIB also comes with some interesting built-in
functions.
unregister(variable)Allow you to de-register the
variables from a particular session. Note that in this case, the variable is not
deleted, though its value will be lost at the end of a page, as it is no longer
saved to the database.
<?php
page_open(array("sess" => "Example_Session"));
// register a variable
$sess->register('username');
// check whether or not it has been registered
if($sess->is_registered('username'))
{
echo "Variable \"username\" is registered!<br>";
}
else
{
echo "Variable \"username\" is unregistered!<br>";
}
// unregister a variable
$sess->unregister('username');
// check whether or not it has been unregistered
if($sess->is_registered('username'))
{
echo "Variable \"username\" is registered!<br>";
}
else
{
echo "Variable \"username\" is unregistered!<br>";
}
page_close();
?>
is_registered(variable)Returns true if the
variable is registered with the session, false otherwise.
<?php
page_open(array("sess" => "Example_Session"));
if($sess->is_registered('username'))
{
echo "A session variable by the name \"username\" already exists";
}
else
{
$sess->register('username');
}
page_close();
?>
delete()Destroy the current session.
An
interesting point to be noted here: In PHPLIB's cookie mode, it's possible to
start a new session after the delete() function has been called, set a new
cookie on the client, and even re-register some of the previous session
variables - essentially changing the session on the fly. Of course, if you do
things like this, you need to get yourself a
life...fast!
url($url)Allows you to redirect users to a new
page.
self_url()Returns a URL referencing the current page,
including PHP_SELF and QUERY_STRING information.{mospagebreak title=The Patient
Has Left The Building}
Patient: Wow, Doc - that was fantastic!
Thanks so much for straightening me out!
Psychiatrist: No problem at all,
Victor. I'm glad I could help. Are you feeling better now?
Patient: Oh,
definitely! When I first came in, the whole day looked gray and depressing -
now, the view from this penthouse window has never looked
better...
Psychiatrist: Ummm...Victor...I'd be careful out there if I
were you. The railing's a little weak, and it might not be safe to go out
there.
Patient: Not to worry, Doc - on a day like this, I feel
invinc...Aaargh!!!!
