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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 database connections, persistent connections have become a common optimization technique. In PHP, the mysqli::real_connect method provides a flexible way to establish persistent connections to the database. This article explores its usage techniques and best practices.
## 1. What Are Persistent Connections
Traditional database connections are closed at the end of each request, and the next request must establish a new connection, which can be time-consuming. Persistent connections, however, are not destroyed when the request ends; instead, they are kept in a connection pool for reuse in subsequent requests, significantly reducing connection overhead.
In mysqli, simply prefixing the hostname with p: enables 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 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 class="hljs-string">'password'</span></span>, </span><span><span class="hljs-string">'database'</span></span>);
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Persistent connections are only triggered when the p: prefix is explicitly specified in the real_connect method. Without it, the connection remains non-persistent.
Handle connection parameters carefully
Persistent connections are cached at a low level. If connection parameters (such as username, password, or database name) are inconsistent, it may cause unnecessary connection pool growth. Always ensure parameters are consistent and appropriate.
Verify connection reuse
After enabling persistent connections, it’s a good idea to check whether the connection is being reused by querying the thread ID, 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
While persistent connections reduce overhead, poor management can still result in too many connections on the database server. It is recommended to configure a reasonable maximum number of connections on the server and apply connection pool strategies.
Avoid long transactions
When persistent connections are reused, uncommitted or unrolled-back transactions from previous requests can affect subsequent ones. Best practice is to ensure all transactions are explicitly completed before the request ends.
Monitor and optimize regularly
The effectiveness of persistent connections depends on the actual application scenario. Regularly monitor database load, connection counts, and application performance, and adjust configurations accordingly.
Using mysqli::real_connect to enable persistent connections can significantly reduce the cost of establishing database connections and improve application response times. However, persistent connections are not a one-size-fits-all solution. Proper configuration and disciplined usage are key to maintaining stability and efficiency. Developers should adapt this technique to their specific scenarios, striking a balance between performance and reliability.
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