<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Start new or resume existing session</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.session-set-save-handler.html">session_set_save_handler</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.session-status.html">session_status</a></div> <div class="up"><a href="ref.session.html">Session Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="function.session-start" class="refentry"> <div class="refnamediv"> <h1 class="refname">session_start</h1> <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">session_start</span> — <span class="dc-title">Start new or resume existing session</span></p> </div> <div class="refsect1 description" id="refsect1-function.session-start-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><strong>session_start</strong></span> ( <span class="methodparam">void</span> )</div> <p class="para rdfs-comment"> <span class="function"><strong>session_start()</strong></span> 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. </p> <p class="para"> When <span class="function"><strong>session_start()</strong></span> 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 <span class="function"><a href="function.session-set-save-handler.html" class="function">session_set_save_handler()</a></span>. 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. </p> <p class="para"> To use a named session, call <span class="function"><a href="function.session-name.html" class="function">session_name()</a></span> before calling <span class="function"><strong>session_start()</strong></span>. </p> <p class="para"> When <a href="session.configuration.html#ini.session.use-trans-sid" class="link">session.use_trans_sid</a> is enabled, the <span class="function"><strong>session_start()</strong></span> function will register an internal output handler for URL rewriting. </p> <p class="para"> If a user uses <em>ob_gzhandler</em> or similar with <span class="function"><a href="function.ob-start.html" class="function">ob_start()</a></span>, the function order is important for proper output. For example, <em>ob_gzhandler</em> must be registered before starting the session. </p> </div> <div class="refsect1 returnvalues" id="refsect1-function.session-start-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> This function returns <strong><code>TRUE</code></strong> if a session was successfully started, otherwise <strong><code>FALSE</code></strong>. </p> </div> <div class="refsect1 changelog" id="refsect1-function.session-start-changelog"> <h3 class="title">Changelog</h3> <p class="para"> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>5.3.0</td> <td> If a session fails to start, then <strong><code>FALSE</code></strong> is returned. Previously <strong><code>TRUE</code></strong> was returned. </td> </tr> <tr> <td>4.3.3</td> <td> As of PHP 4.3.3, calling <span class="function"><strong>session_start()</strong></span> after the session was previously started will result in an error of level <strong><code>E_NOTICE</code></strong>. Also, the second session start will simply be ignored. </td> </tr> </tbody> </table> </p> </div> <div class="refsect1 examples" id="refsect1-function.session-start-examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example" id="example-4772"> <p><strong>Example #1 A session example: <var class="filename">page1.php</var></strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// page1.php<br /><br /></span><span style="color: #0000BB">session_start</span><span style="color: #007700">();<br /><br />echo </span><span style="color: #DD0000">'Welcome to page #1'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'favcolor'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'green'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'animal'</span><span style="color: #007700">] = </span><span style="color: #DD0000">'cat'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'time'</span><span style="color: #007700">] = </span><span style="color: #0000BB">time</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// Works if session cookie was accepted<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'<br /><a href="page2.php">page 2</a>'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Or maybe pass along the session id, if needed<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'<br /><a href="page2.php?' </span><span style="color: #007700">. </span><span style="color: #0000BB">SID </span><span style="color: #007700">. </span><span style="color: #DD0000">'">page 2</a>'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> </div> </p> <p class="para"> After viewing <var class="filename">page1.php</var>, the second page <var class="filename">page2.php</var> will magically contain the session data. Read the <a href="ref.session.html" class="link">session reference</a> for information on <a href="session.idpassing.html" class="link">propagating session ids</a> as it, for example, explains what the constant <strong><code>SID</code></strong> is all about. </p> <p class="para"> <div class="example" id="example-4773"> <p><strong>Example #2 A session example: <var class="filename">page2.php</var></strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// page2.php<br /><br /></span><span style="color: #0000BB">session_start</span><span style="color: #007700">();<br /><br />echo </span><span style="color: #DD0000">'Welcome to page #2<br />'</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'favcolor'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// green<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'animal'</span><span style="color: #007700">]; </span><span style="color: #FF8000">// cat<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">date</span><span style="color: #007700">(</span><span style="color: #DD0000">'Y m d H:i:s'</span><span style="color: #007700">, </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'time'</span><span style="color: #007700">]);<br /><br /></span><span style="color: #FF8000">// You may want to use SID here, like we did in page1.php<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'<br /><a href="page1.php">page 1</a>'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> </div> </p> </div> <div class="refsect1 notes" id="refsect1-function.session-start-notes"> <h3 class="title">Notes</h3> <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para"> To use cookie-based sessions, <span class="function"><strong>session_start()</strong></span> must be called before outputing anything to the browser. </p> </p></blockquote> <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para"> Use of <a href="zlib.configuration.html#ini.zlib.output-compression" class="link">zlib.output_compression</a> is recommended instead of <span class="function"><a href="function.ob-gzhandler.html" class="function">ob_gzhandler()</a></span> </p> </p></blockquote> <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para"> This function sends out several HTTP headers depending on the configuration. See <span class="function"><a href="function.session-cache-limiter.html" class="function">session_cache_limiter()</a></span> to customize these headers. </p> </p></blockquote> </div> <div class="refsect1 seealso" id="refsect1-function.session-start-seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><var class="varname"><var class="varname"><a href="reserved.variables.session.html" class="classname">$_SESSION</a></var></var></li> <li class="member"> The <a href="session.configuration.html#ini.session.auto-start" class="link">session.auto_start</a> configuration directive </li> <li class="member"> <span class="function"><a href="function.session-id.html" class="function" rel="rdfs-seeAlso">session_id()</a> - Get and/or set the current session id</span></li> </ul> </p> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.session-set-save-handler.html">session_set_save_handler</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.session-status.html">session_status</a></div> <div class="up"><a href="ref.session.html">Session Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>