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# Implementing Persistent Connections with mysqli::real_connect: Tips and Best Practices
In high-concurrency web applications, database connections are often one of the main performance bottlenecks. To reduce the overhead of frequently creating and closing connections, persistent connections are a common optimization technique. In PHP, the mysqli::real_connect method provides a flexible way to establish persistent database connections. This article explores its usage tips and best practices.
## I. What is a Persistent Connection
Traditional database connections are closed at the end of each request, and the next request needs to establish a new connection, which can be costly. Persistent connections, on the other hand, are not destroyed at the end of a request. Instead, they are retained in a connection pool and reused by subsequent requests, significantly reducing the cost of connection establishment.
In mysqli, you only need to add the prefix p: before the hostname to enable persistent connections. For example:
</span><span><span class="hljs-variable">$mysqli</span></span><span> = </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-title function_ invoke__">mysqli</span></span><span>();
</span><span><span class="hljs-variable">$mysqli</span></span>-></span><span><span class="hljs-title function_ invoke__">real_connect</span></span><span>(</span><span><span class="hljs-string">'p:localhost'</span></span><span>, </span><span><span class="hljs-string">'user'</span></span><span>, </span><span><span class="hljs-string">'password'</span></span>, </span><span><span class="hljs-string">'database'</span></span><span>);
</span></span>
Persistent connections are only triggered when you explicitly add the p: prefix in the real_connect method. If you forget to include it, the connection will remain a regular non-persistent one.
Handle connection parameters carefully
Persistent connections are cached at a lower level. If connection parameters (such as username, password, or database name) differ, it may lead to unnecessary connection pool expansion. Therefore, parameters should be consistent and well-managed.
Check whether the connection was reused
After enabling persistent connections, it’s a good practice to confirm whether a connection is being reused by checking the thread ID or similar indicators. For example:
<span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Thread ID: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span>->thread_id;
</span></span>Combine with connection pool management
Although persistent connections reduce overhead, poor management can result in too many open connections on the database server. It’s recommended to configure reasonable maximum connections on the server side and use a connection pool strategy.
Avoid long transactions
When persistent connections are reused, uncommitted or unrolled-back transactions from a previous request could affect the next one. Best practice is to explicitly end all transactions before completing each request.
Regular monitoring and tuning
The effectiveness of persistent connections should be evaluated in real-world scenarios. Monitor database load, number of connections, and application performance regularly, and adjust whether to enable or fine-tune configurations as needed.
Enabling persistent connections through mysqli::real_connect can significantly reduce the cost of establishing database connections and improve application response time. However, persistent connections are not a one-size-fits-all solution. Proper configuration and disciplined usage are key to ensuring system stability and efficiency. Developers should adapt this technique to their specific use cases, striking the right balance between performance and reliability.
<span></span>Related Tags:
mysqli