Page 321 - Beginning PHP 5.3

Chapter 10: Preserving State With Query Strings
to the browser as a cookie called PHPSESSID (by default). However, if the browser has sent a PHPSESSID
cookie to the server because a session already exists, session_start() uses this existing session:
session_start();
There ’ s one gotcha though: because session_start() needs to send the PHPSESSID cookie in an HTTP
header when it creates a session, you must call it before you output anything to the browser, much like
you do with setcookie() :
Hi there!
< ?php
// Generates a “Cannot send session cookie - headers already sent” warning
session_start();
? >

Reading and Writing Session Data

Working with session data in PHP is also simple. You store all your session data as keys and values in
the $_SESSION[] superglobal array. So you might store the user ’ s first name using:

$_SESSION[“firstName”] = “John”;
You could then display the user ’ s first name — whether in the same page request or during a later
request — as follows:

echo( $_SESSION[“firstName”] );

You can store any type of data in sessions, including arrays and objects:

$userDetails = array( “firstName” => “John”, “lastName” => “Smith”, “age” =>
34 );
$_SESSION[“userDetails”] = $userDetails;

However, if storing objects make sure you include your class definitions (or class definition files) before
trying to retrieve the objects from the $_SESSION array, so that the PHP engine can correctly identify the
objects when they ’ re retrieved:
session_start();

class WebUser {
public $firstName;
public $lastName;
}
if ( isset( $_SESSION[“user”] ) ) {
// Make sure the WebUser class is defined by this point
print_r( $_SESSION[“user”] );
} else {
echo “Creating user...”;
$user = new WebUser;

$user-> firstName = “John”;

$user-> lastName = “Smith”;
$_SESSION[“user”] = $user;

}

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