php man page for session_start

SESSION_START(3)							 1							  SESSION_START(3)

session_start - Start new or resume existing session

SYNOPSIS
       bool session_start (void  )

DESCRIPTION
       session_start(3) creates a session or resumes the current one based on a session identifier passed via a GET or POST request, or passed via
       a cookie.

	When session_start(3) is called or when a session auto starts, PHP will call the open and read session save handlers. These will either be
       a built-in save handler provided by default or by PHP extensions (such as SQLite or Memcached); or can be custom handler as defined by ses-
       sion_set_save_handler(3). The read callback will retrieve any existing session data (stored in a special serialized  format)  and  will	be
       unserialized and used to automatically populate the $_SESSION superglobal when the read callback returns the saved session data back to PHP
       session handling.

	To use a named session, call session_name(3) before calling session_start(3).

	When session.use_trans_sid is enabled, the session_start(3) function will register an internal output handler for URL rewriting.

	If a user uses ob_gzhandler or similar with ob_start(3), the function order is important for proper output. For example, ob_gzhandler must
       be registered before starting the session.

RETURN VALUES
	This function returns TRUE if a session was successfully started, otherwise FALSE.

CHANGELOG
       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.3.0	|						    |
       |	|						    |
       |	|  If  a  session  fails  to  start,  then FALSE is |
       |	| returned. Previously TRUE was returned.	    |
       |	|						    |
       | 4.3.3	|						    |
       |	|						    |
       |	|  As of PHP 4.3.3, calling session_start(3)  after |
       |	| the session was previously started will result in |
       |	| an error of level E_NOTICE. Also, the second ses- |
       |	| sion 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

	       To use cookie-based sessions, session_start(3) must be called before outputing anything to the browser.

       Note

	       Use of zlib.output_compression is recommended instead of ob_gzhandler(3)

       Note

	       This function sends out several HTTP headers depending on the configuration. See session_cache_limiter(3) to customize these  head-
	      ers.

SEE ALSO
       $_SESSION,  The session.auto_start configuration directive , session_id(3).

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