mysqli_stmt::attr_get return value detailed explanation and common types

In PHP's MySQLi extension, mysqli_stmt::attr_get is a method used to obtain the value of the prepared statement attribute. Understanding its return value type and practical application skills is crucial to developing efficient and stable database operation code. This article will analyze the return value type of mysqli_stmt::attr_get in detail, and combine it with common usage scenarios to help you better master this function.

1. Introduction to mysqli_stmt::attr_get

mysqli_stmt::attr_get is a method of MySQLi preprocessing statement object, which is used to obtain the current value of a certain attribute. Its definition is as follows:

 public int|bool mysqli_stmt::attr_get(int $attr)

where $attr is an integer representing the attribute identifier to be retrieved.

2. Return value type analysis

There are two main types of value returned by mysqli_stmt::attr_get:

• Int : Returns the value of the attribute, such as maximum packet size, timeout time, etc.

• Boolean : indicates whether the attribute is enabled or supported.

In actual applications, most properties return integers, but depending on the properties, they may also return boolean values.

3. Common properties and corresponding return value types

Some common attributes supported by MySQLi for attr_get are as follows:

4. Code example

Here is an actual PHP code example that demonstrates how to use mysqli_stmt::attr_get and process the return value:

 <?php
$mysqli = new mysqli("m66.net", "username", "password", "database");

if ($mysqli->connect_error) {
    die("Connection failed: " . $mysqli->connect_error);
}

$stmt = $mysqli->prepare("SELECT * FROM users WHERE id = ?");
if (!$stmt) {
    die("Preprocessing statement creation failed: " . $mysqli->error);
}

// Get the prefetched row count attribute
$prefetchRows = $stmt->attr_get(MYSQLI_STMT_ATTR_PREFETCH_ROWS);
echo "Number of lines: " . $prefetchRows . PHP_EOL;

// Get cursor type
$cursorType = $stmt->attr_get(MYSQLI_STMT_ATTR_CURSOR_TYPE);
echo "Cursor type: " . $cursorType . PHP_EOL;

// Get whether to allow updating the maximum length
$updateMaxLength = $stmt->attr_get(MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH);
echo "Allow updates to the maximum length: " . ($updateMaxLength ? 'yes' : 'no') . PHP_EOL;

$stmt->close();
$mysqli->close();
?>

5. Practical application skills

• Error handling : attr_get does not throw an exception on failure, but the returned value may not be as expected. It is recommended to combine mysqli_stmt::error to monitor the status.

• Property selection : Not all properties can be used in all MySQL versions and drivers. It is recommended to view the list of properties supported by the current environment.

• Performance considerations : The overhead of reading attributes is low, but frequent calls to unnecessary attribute acquisition will also affect performance and be used reasonably.

6. Summary

The return value type of mysqli_stmt::attr_get is mostly an integer or a boolean, depending on the obtained attribute type. Mastering the meaning of these return values ​​and attributes can help write more robust database access code. Combining actual business needs and using this method reasonably can improve the flexibility and maintainability of the code.