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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Passing the Session ID</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="session.examples.html">Examples</a></div> <div class="next" style="text-align: right; float: right;"><a href="session.customhandler.html">Custom Session Handlers</a></div> <div class="up"><a href="session.examples.html">Examples</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="session.idpassing" class="section"> <h2 class="title">Passing the Session ID</h2> <p class="para"> There are two methods to propagate a session id: <ul class="itemizedlist"> <li class="listitem"> <span class="simpara"> Cookies </span> </li> <li class="listitem"> <span class="simpara"> URL parameter </span> </li> </ul> </p> <p class="para"> The session module supports both methods. Cookies are optimal, but because they are not always available, we also provide an alternative way. The second method embeds the session id directly into URLs. </p> <p class="para"> PHP is capable of transforming links transparently. Unless you are using PHP 4.2.0 or later, you need to enable it manually when building PHP. Under Unix, pass <a href="session.configuration.html#ini.session.use-trans-sid" class="link"> --enable-trans-sid</a> to configure. If this build option and the run-time option <i>session.use_trans_sid</i> are enabled, relative URIs will be changed to contain the session id automatically. <blockquote><p><b class="note">Note</b>: The <a href="ini.core.html#ini.arg-separator.output" class="link">arg_separator.output</a> <var class="filename">php.ini</var> directive allows to customize the argument seperator. For full XHTML conformance, specify &amp; there. <br /> </p></blockquote> </p> <p class="para"> Alternatively, you can use the constant <i>SID</i> which is defined if the session started. If the client did not send an appropriate session cookie, it has the form <i>session_name=session_id</i>. Otherwise, it expands to an empty string. Thus, you can embed it unconditionally into URLs. </p> <p class="para"> The following example demonstrates how to register a variable, and how to link correctly to another page using SID. <div class="example"> <p><b>Example #1 Counting the number of hits of a single user</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /><br />session_start</span><span style="color: #007700">();<br /><br />if (empty(</span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'count'</span><span style="color: #007700">])) {<br /> </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'count'</span><span style="color: #007700">] = </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />} else {<br /> </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'count'</span><span style="color: #007700">]++;<br />}<br /></span><span style="color: #0000BB">?><br /></span><br /><p><br />Hello visitor, you have seen this page <span style="color: #0000BB"><?php </span><span style="color: #007700">echo </span><span style="color: #0000BB">$_SESSION</span><span style="color: #007700">[</span><span style="color: #DD0000">'count'</span><span style="color: #007700">]; </span><span style="color: #0000BB">?></span> times.<br /></p><br /><br /><p><br />To continue, <a href="nextpage.php?<span style="color: #0000BB"><?php </span><span style="color: #007700">echo </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">SID</span><span style="color: #007700">); </span><span style="color: #0000BB">?></span>">click<br />here</a>.<br /></p></span></code></div> </div> </div> </p> <p class="para"> The <a href="function.htmlspecialchars.html" class="function">htmlspecialchars()</a> may be used when printing the SID in order to prevent XSS related attacks. </p> <p class="para"> Printing the SID, like shown above, is not necessary if <a href="session.configuration.html#ini.session.use-trans-sid" class="link"> --enable-trans-sid</a> was used to compile PHP. </p> <blockquote><p><b class="note">Note</b>: Non-relative URLs are assumed to point to external sites and hence don't append the SID, as it would be a security risk to leak the SID to a different server. <br /> </p></blockquote> </div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="session.examples.html">Examples</a></div> <div class="next" style="text-align: right; float: right;"><a href="session.customhandler.html">Custom Session Handlers</a></div> <div class="up"><a href="session.examples.html">Examples</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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