Encoding/Decoding Session Data

PHP stores all the session data associated with a session ID in a single string and handles the
decoding of this string automatically. However, there are times when it may be necessary or
beneficial to handle this process manually. The first thing to understand is how the string is put
together. In the following example, three session variables are stored (last name, first name and
phone number):

lname|s:6:"Gordon";fname|s:6:"Jethro";phone|s:10:"7197235674";

The session variables are separated by a semicolon (;) and then can be broken down into their
individual components: name of the variable, length of the string that is contained and the value
itself. For the session variable lname, the length of the string is 6 characters long and the value
that is stored in the string is "Gordon".

Encoding the Session Variables

The function session_encode allows for all the session variables available to the user to be
encoded into a single string (as shown above). This can be helpful in the event that a developer
may wish to store this string into a database and later retrieve it.

<?php
session_start();
// Load the session variables with values
$_SESSION['lname'] = 'Gordon';
$_SESSION['fname'] = 'Jethro';
$_SESSION['phone'] = '7197235674';
// Combine all the session variables together
// into a single string
$session_variables = session_encode();
?>

Decoding the Session Variables

The manual decoding process is as simple as the encoding process when using the
session_decode() function. This function takes one input parameter; the variable that is storing
the encoded session variable string. When decoded, each value will be placed into its
corresponding session variable.

<?php
session_start();
// Obtain the Session ID from the local system
$SID = session_id();
// Read in the encoded session string from MySQL
$linkID1 = mysql_connect("localhost", "root", "training");
$session_query = "SELECT sessionVars FROM world.user
WHERE sid = $SID";
$session_result = mysql_query($session_query, $linkID1);
list($session_variables) = mysql_fetch_row($session_result);
session_decode($session_variables);
print "Name: ".$_SESSION['lname'].", ".$_SESSION['fname'];
print " Phone: ".$_SESSION['phone']."<br>\n";
mysql_close($linkID1);
?>