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Market Game

Now that you know the basics, let’s get a little more complex and demonstrate a real-life session application. Let's assume for a moment that you have a financial portal that allows its user to select four stocks and then displays the current market price of each stock and displays on each page the user's progress on the site.

In the following example, we assume that the user has been authenticated and logged in to the site. We used a MySQL database, which has a table named user_info, which is used to store the user's four stocks and unique user name. Once a session is initialized, we register variables to hold the username and four stocks, then connect to the database to retrieve the values ​​and display them on the page.

The code is as follows:

$#@60;?php

//Initialize a session session_start();

//Register session variable

//User name
session_register (username);

//Selected stock variables
session_register(stock1);
session_register(stock2);
session_register(stock3);
session_register(stock4);

//Connect to MySQL
$db = mysql_connect("someserver.com", "tom", "jones");

//Select database
mysql_select_db("stock_db", $db);

//Use SQL to query the database
$query = "select stock_pref1,stock_pref2,stock_pref3,stock_pref4
from user_info where username=$username";

$ result = mysql_query($query,$db);

//Get the stock code from the database and assign it to the session variable
list($stock1,$stock2,$stock3,$stock4) = mysql_fetch_row ($result);

echo "Hi $username!$#@60;br$#@62;";
echo "Your selected stocks are:$#@60;br$#@62 ;";
echo "$stock1$#@60;br$#@62;";
echo "$stock2$#@60;br$#@62;";
echo "$stock3 $#@60;br$#@62;";
echo "$stock4$#@60;br$#@62;";

// code to generate rest of page

?$#@62;

PHP4 has many session-related functions - most of which require no explanation, so they are listed below.

session_destroy(): Release all session data (very useful when a user logs out of a site, you need to release all variables created during his visit).

session_name():Set or read the name of the current session.

session_id():Set or read the id value of the current session.
session_unregister(session_variable_name):Unregister a variable from a particular session.

session_is_registered(): Check whether a session variable has been registered.

For example:

$#@60;?php

session_start();

if(session_is_registered(username))
{
echo "A session variable by the name "username "
already exists";
}
else
{
echo "No variable named "username" registered yet.
Registering...";
session_register(username) ;
}

?$#@62;

session_encode() and session_decode():Encode session data into a string or decode a string into session data.

Here you may use them:

$#@60;?php

session_start();

session_register(someString);
$someString="I hate cats!";

//Compile all session variables into a string
$sessStr = session_encode();

//You can see it here
echo $sessStr;

echo " $#@60;br$#@62;$#@60;br$#@62;";

//Replace with dogs where cats appear
$sessStr = ereg_replace(" cats","dogs",$sessStr);

//The session variable is updated after decoding
session_decode($sessStr);

//Display $sessstr again
echo $someString;

?$#@62;

Finally, before starting PHPLIB, there is a technical issue you should be aware of - all the examples above use cookies to save the session id value on the client side. But what happens if the user's browser is set to reject cookies?

If this happens, a session id needs to be passed from one page to another by embedding it in the URL. For example: $#@60;a href="http://www.someserver.com/admin/preferences.php3?PHPSESSID=$#@60;? echo "$PHPSESSID"; ?$#@62;"$# @62;Edit Your Portfolio! $#@60;/a$#@62;

This can ensure that the session variable is valid in subsequent pages.