session_set_save_handler
session_unregister
Sessions Functions
PHP Manual

# session_start

(PHP 4, PHP 5)

session_start — Initialize session data

### Description

bool session_start ( void )

session_start() creates a session or resumes the current one based on the current session id that's being passed via a request, such as GET, POST, or a cookie.

If you want to use a named session, you must call session_name() before calling session_start().

session_start() will register internal output handler for URL rewriting when trans-sid is enabled. If a user uses ob_gzhandler or like with ob_start(), the order of output handler is important for proper output. For example, user must register ob_gzhandler before session start.

### Return Values

This function always returns `TRUE`.

### ChangeLog

Version | Description
--- | ---
4.3.3 | As of now, calling session_start() while the session has already been started will result in an error of level `E_NOTICE`. Also, the second session start will simply be ignored.

### Examples

Example#1 A session example: page1.php

`<?php
// page1.php
session_start();
echo 'Welcome to page #1';
$_SESSION['favcolor'] = 'green';
$_SESSION['animal'] = 'cat';
$_SESSION['time'] = time();
// Works if session cookie was accepted
echo '<br /><a href="page2.php">page 2</a>';
// Or maybe pass along the session id, if needed
echo '<br /><a href="page2.php?' . SID . '">page 2</a>';
?>`

After viewing page1.php, the second page page2.php will magically contain the session data. Read the session reference for information on propagating session ids as it, for example, explains what the constant `SID` is all about.

Example#2 A session example: page2.php

`<?php
// page2.php
session_start();
echo 'Welcome to page #2<br />';
echo $_SESSION['favcolor']; // green
echo $_SESSION['animal']; // cat
echo date('Y m d H:i:s', $_SESSION['time']);
// You may want to use SID here, like we did in page1.php
echo '<br /><a href="page1.php">page 1</a>';
?>`

### Notes

> Note: If you are using cookie-based sessions, you must call session_start() before anything is outputted to the browser.

> Note: Use of zlib.output_compression is recommended rather than ob_gzhandler()

### See Also

- $_SESSION
- The session.auto_start configuration directive
- session_id()

session_set_save_handler
session_unregister
Sessions Functions
PHP Manual