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When using PHP to manipulate MySQL databases, the mysqli extension provides an object-oriented interface to improve the readability and maintainability of the code. Among them, the mysqli_stmt class is the core component that executes preprocessing statements. In scenarios where high concurrency or optimization performance is required, developers often choose to use Persistent Connection to avoid the overhead of repeatedly establishing database connections.
In this context, how does the mysqli_stmt::attr_get method perform? This article will discuss this issue in depth.
mysqli_stmt::attr_get is a method in the mysqli_stmt class that gets some attribute values of a preprocessing statement object. For example:
$stmt = $mysqli->prepare("SELECT * FROM users WHERE id = ?");
$timeout = $stmt->attr_get(MYSQLI_STMT_ATTR_QUERY_TIMEOUT);
This method is often used to obtain attribute values such as query timeout ( MYSQLI_STMT_ATTR_QUERY_TIMEOUT ) for dynamic adjustment or debug optimization.
Persistent connections are when the request is finished, instead of closing the database connection, but keeping the connection in the process for reuse of the next request. In PHP, persistent connections are usually achieved by prefixing the hostname with a p: prefix:
$mysqli = new mysqli("p:m66.net", "user", "password", "dbname");
This can significantly reduce the performance loss caused by frequent connections and disconnection of databases, especially for applications with high frequency access.
According to a lot of tests and community feedback, mysqli_stmt::attr_get behaves almost the same as non-persistent connections in a persistent connection environment. That is, it can accurately return the current value of the specified property without being disturbed by the persistence mechanism.
However, the following points need to be noted:
The scope of attribute values is still limited to the current statement object <br> Whether it is a persistent connection or not, the attributes obtained through attr_get are only applicable to the current mysqli_stmt instance and do not affect other statements or global settings.
Each time prepare, a new statement object will still be generated <br> Even if the connection is persistent, the system will still create a brand new statement object when calling prepare() . Attr_get gets the attributes of the object, so the status from the previous request will not be left behind.
No direct cache effect with persistent connections
Attr_get is essentially reading the status of the current statement object and does not involve server state cache. Therefore, even if the connection is multiplexed, the attribute value still takes effect according to the actual setting. For example, if you set the MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH property, it still needs to be explicitly set before prepare and cannot rely on persistent connections for "inheritance".
Although attr_get itself is a lightweight operation, in a persistent connection environment, resources may not be released in time, such as the statement handle not being closed, resulting in increased memory usage. Therefore, it is recommended:
After using the statement object, be sure to call $stmt->close() ;
Avoid the heavy use of unreleased preprocessing statements in loops;
Combining attr_get and attr_set to achieve more refined statement control to improve query efficiency.
Overall, mysqli_stmt::attr_get performs stably and consistently in persisted connections, with no compatibility or behavioral differences. Developers can be assured to use attr_get to obtain statement attributes while using persistent connections to achieve more flexible database operation logic.
However, when using persistent connections, you need to pay extra attention to resource management and state cleaning in order to truly leverage its performance advantages and avoid unexpected memory or connection leakage problems.
