11 Session and data retention

1 Maintain user information in the website through SessionID

<code><span><span><?php</span>
session_start();
<span>$_SESSION</span>[<span>'visits'</span>]++;
<span>print</span><span>'You have visited here '</span>.<span>$_SESSION</span>[<span>'visits'</span>].<span>' times.<br>'</span>;
<span>echo</span><span>'session id = '</span>.<span>$_COOKIE</span>[<span>'PHPSESSID'</span>];
<span>echo</span><span>"<br>"</span>;
<span>echo</span><span>"session name = "</span>.session_name().<span>"<br>"</span>;
<span>?></span></span></code>

SessionID is recorded in the global variable _COOKIE. The name of SessionID is PHPSESSID, and PHPSESSID can also be obtained through session_name().

2 Prevent Session Hijacking

<code><span><span><span><?php</span>
ini_set(<span>'sessio.use_only_cookies'</span>, <span>true</span>);
session_start();
<span>$salt</span> = <span>'YourSpecialValueHere'</span>;
<span>$tokenstr</span> = date(<span>'W'</span>).<span>$salt</span>;
<span>$token</span> = md5(<span>$tokenstr</span>);
<span>echo</span><span>'token = '</span>.<span>$token</span>.<span>'<br>'</span>;

<span>if</span>(!<span>isset</span>(<span>$_REQUEST</span>[<span>'token'</span>]) || <span>$_REQUEST</span>[<span>'token'</span>] != <span>$token</span>)
{
    <span>exit</span>;
}
<span>$_SESSION</span>[<span>'token'</span>] = <span>$token</span>;
output_add_rewrite_var(<span>'token'</span>, <span>$token</span>);
<span>echo</span><span>'<a href="test.php">link</a>'</span>;
ob_flush();
output_reset_rewrite_vars();
<span>?></span></span></span></code>

<code><span><span><span><?php</span>
session_start();
output_add_rewrite_var(<span>'var'</span>, <span>'value'</span>);

<span>echo</span><span>'<a href="file.php">link</a>'</span>;
ob_flush();

output_reset_rewrite_vars();
<span>echo</span><span>'<a href="file.php">link</a>'</span>;
<span>?></span></span>以上例程会输出：

<span><<span>a</span><span>href</span>=<span>"file.php?PHPSESSID=xxx&var=value"</span>></span>link<span></<span>a</span>></span><span><<span>a</span><span>href</span>=<span>"file.php"</span>></span>link<span></<span>a</span>></span></span></code>

3 Prevent Session Customization

• Will not append the session identifier to the session cookie on the URL.
• Frequently generate new session ID

<code><span><span><?php</span>
ini_set(<span>'session.use_only_cookie'</span>, <span>true</span>);
session_start();
<span>if</span>(!<span>isset</span>(<span>$_SESSION</span>[<span>'generated'</span>]) || <span>$_SESSION</span>[<span>'generated'</span>] < (time() - <span>30</span>))
{
    session_regenerate_id();
    <span>$_SESSION</span>[<span>'generated'</span>] = time();
}
<span>echo</span><span>$_COOKIE</span>[<span>'PHPSESSID'</span>]</span></code>

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The above has introduced 11 Session and data retention, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.