What Does session_cache_expire Do in PHP? A Detailed Introduction to Its Basic Usage

gitbox 2025-07-17

In PHP, the session_cache_expire function is used to set the duration of the session cache expiration. Session cache is designed to improve the efficiency of accessing session data, particularly when session data is stored using files. The session_cache_expire function lets us control the lifetime of cache files, thereby optimizing performance and preventing unnecessary cache expiration.

1. The Purpose of session_cache_expire

session_cache_expire sets the expiration time of PHP's session cache in minutes. This means that if you use file-based session storage (the default file-based session handling method), the cache files will be considered expired after the set time and need to be regenerated. This is very useful for applications that heavily rely on sessions because it controls when cache files are updated or removed, preventing excessive server load.

2. Function Prototype

<span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-title function_ invoke__">session_cache_expire</span></span><span> ( </span><span><span class="hljs-keyword">void</span></span><span> )
</span></span>

This form of the function retrieves the current session cache expiration time. It returns an integer representing the expiration time in minutes.

<span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-title function_ invoke__">session_cache_expire</span></span><span> ( </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$new_cache_expire</span></span><span> )
</span></span>

When an integer parameter is passed, session_cache_expire sets the session cache expiration time to the specified number of minutes.

3. Usage Examples

Suppose you are developing a website and want the cache expiration time to be 30 minutes. You can use session_cache_expire to set the cache expiration, ensuring that session data expires and regenerates after 30 minutes.

Example 1: Getting the Session Cache Expiration Time

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// Get the current session cache expiration time</span>
</span><span><span class="hljs-variable">$current_expire</span></span><span> = </span><span><span class="hljs-title function_ invoke__">session_cache_expire</span></span><span>();
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Current session cache expiration time: <span class="hljs-subst">$current_expire</span></span> minutes";
</span><span><span class="hljs-meta">?&gt;</span>
</span></span>

This code outputs the current session cache expiration time in minutes.

Example 2: Setting the Session Cache Expiration Time

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// Set the session cache expiration time to 30 minutes</span>
</span><span><span class="hljs-title function_ invoke__">session_cache_expire</span></span><span>(</span><span><span class="hljs-number">30</span></span><span>);
</span><span>
</span><span><span class="hljs-comment">// Start the session</span>
</span><span><span class="hljs-title function_ invoke__">session_start</span></span><span>();
</span><span>
</span><span><span class="hljs-comment">// Set some session data</span>
</span><span><span class="hljs-variable">$_SESSION</span></span><span>[</span><span><span class="hljs-string">'user'</span></span><span>] = </span><span><span class="hljs-string">'John Doe'</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Session data stored; cache will expire in 30 minutes."</span></span>;
</span><span><span class="hljs-meta">?&gt;</span>
</span></span>

In this example, we set the session cache expiration time to 30 minutes, then start the session and store some simple user data.

4. Important Notes

session_cache_expire sets the expiration time for the session cache files, but it does not affect the lifetime of the session itself. Even if the cache files expire, PHP session data (such as contents stored via $_SESSION) can still be used until the session ends or is explicitly destroyed.
If you do not explicitly call session_cache_expire to set the expiration time, PHP will use the default value of 180 minutes (3 hours).
session_cache_expire is only effective when files are used for session storage. If other storage mechanisms like databases or memory are used, expiration may follow different rules.

5. Advanced Usage

If you are developing a high-load application or have a complex session storage environment on your server, session_cache_expire can help you avoid unnecessary cache expiration. By adjusting the expiration time, you can balance performance with session data validity.

Summary

session_cache_expire is a PHP function used to set the expiration time of session cache. It helps developers control the lifecycle of session cache files, improving performance and reducing the burden caused by excessive cache files. In most cases, setting a reasonable session cache expiration time is crucial for application responsiveness and resource utilization.

session_cache_expire