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What are the common reasons for mysqli::$server_info returning an empty value, and what are the common errors and corresponding solutions?

gitbox 2025-06-21 
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// This part of the code is unrelated to the article content, used as a placeholder for example</span></span><span>]]]

In the above code, if $mysqli->connect_error is not empty, it indicates a connection failure, and at this point, $mysqli->server_info may return empty.

Common Errors

1: Incorrect connection details leading to connection failure

For example, incorrect username or password, wrong database address, etc.

Common Errors

2: Accessing properties when the connection was unsuccessful

Accessing $mysqli->server_info directly without checking whether the connection is successful.

Common Errors

3: Object state anomaly in multi-threaded or asynchronous environments

The mysqli object state is unstable, which could lead to abnormal property reading.

Solutions

  1. Ensure the connection is successful before accessing server_info
    Use $mysqli->connect_error or $mysqli->connect_errno to check the connection status.
  2. Use exception handling
    Enable mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); to catch errors and avoid silent failures.
  3. Ensure the MySQL server is running correctly
    Check the database server status and confirm the version information is available.
  4. Avoid accessing properties after the connection is closed
    Ensure relevant properties are used before calling close() to avoid object state anomalies.

Improved Code Example

</span><span><span class="hljs-title function_ invoke__">mysqli_report</span></span><span>(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

</span><span><span class="hljs-keyword">try</span></span><span> {
    </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-string">&#039;localhost&#039;</span></span><span>, </span><span><span class="hljs-string">&#039;user&#039;</span></span><span>, </span><span><span class="hljs-string">&#039;password&#039;</span></span><span>, </span><span><span class="hljs-string">&#039;database&#039;</span></span>);

    </span><span><span class="hljs-comment">// Check if connection is successful</span></span>
    </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$mysqli</span></span><span>->connect_errno) {
        </span><span><span class="hljs-keyword">throw</span></span><span> </span><span><span class="hljs-keyword">new</span></span><span> </span><span><span class="hljs-built_in">Exception</span></span><span>(</span><span><span class="hljs-string">"Connection failed: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>->connect_error);
    }

    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"MySQL server version: "</span></span><span> . </span><span><span class="hljs-variable">$mysqli</span></span><span>->server_info;

    </span><span><span class="hljs-variable">$mysqli</span></span><span>-></span><span><span class="hljs-title function_ invoke__">close</span></span><span>();
} </span><span><span class="hljs-keyword">catch</span></span><span> (</span><span><span class="hljs-built_in">Exception</span></span> </span><span><span class="hljs-variable">$e</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Error message: "</span></span><span> . </span><span><span class="hljs-variable">$e</span></span><span>-></span><span><span class="hljs-title function_ invoke__">getMessage</span></span><span>();
}

Conclusion

When mysqli::$server_info returns an empty value, the first thing to check is whether the MySQL connection is successful, as this is the most common cause. Next, be cautious about when you access this property, ensuring the mysqli object is in a valid connection state. Finally, using error reporting and exception handling mechanisms properly can help quickly identify and resolve the problem.

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