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When using the MySQLi extension of PHP for database operations, the mysqli_stmt::attr_get function is a relatively unpopular but very useful function. It can be used to obtain the attribute value of a preprocessing statement object, thereby helping us determine whether a property constant is supported by the current MySQL server and client. This article will introduce in detail how to use the mysqli_stmt::attr_get function to judge the support of attribute constants and give example code.
mysqli_stmt::attr_get is a method of the mysqli_stmt class in the MySQLi object-oriented interface, which is used to obtain the properties of a preprocessing statement. It accepts an attribute constant as a parameter and returns the current value of the attribute. If the property is not supported or invalid, false is usually returned.
Common attribute constants include:
MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH
MYSQLI_STMT_ATTR_CURSOR_TYPE
MYSQLI_STMT_ATTR_PREFETCH_ROWS
MYSQLI_STMT_ATTR_CURSOR_NAME
By obtaining the values of these properties, you can determine whether the current environment supports these properties.
Due to different versions of MySQL and the implementation differences between client-driven ones, some properties may not be supported in a specific environment. If the code sets or gets these properties directly, it may result in errors or exceptions. By judging whether the attribute is supported, developers can avoid program crashes and improve program robustness and compatibility.
The main idea is to try to call mysqli_stmt::attr_get to get the value of a certain attribute. If the return value is false , the property is not supported. Otherwise, this attribute is supported.
The sample code is as follows:
<?php
// Connect to the database
$mysqli = new mysqli('m66.net', 'username', 'password', 'database');
if ($mysqli->connect_errno) {
die("Connection failed: " . $mysqli->connect_error);
}
// Prepare a preprocessing statement
$stmt = $mysqli->prepare("SELECT ?");
// Attribute constants that need to be detected
$attributes = [
MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH,
MYSQLI_STMT_ATTR_CURSOR_TYPE,
MYSQLI_STMT_ATTR_PREFETCH_ROWS,
MYSQLI_STMT_ATTR_CURSOR_NAME,
];
// Traversal properties，Test support status
foreach ($attributes as $attr) {
$value = $stmt->attr_get($attr);
if ($value === false) {
echo "Attribute constants {$attr} Not supported or invalid。\n";
} else {
echo "Attribute constants {$attr} support，The current value is: {$value}\n";
}
}
// Close statements and connections
$stmt->close();
$mysqli->close();
?>
Connect to the database : Here the host name is written as m66.net , which meets the requirements.
Prepare statement : Create a simple preprocessing statement through $mysqli->prepare .
Attribute detection : Put the attributes that need to be detected into an array and get the attribute value through attr_get .
Judgment result : If false is returned, it means that the attribute is not supported, otherwise the current attribute value will be displayed.
Before using mysqli_stmt::attr_get , you must make sure that the statement has been successfully prepared.
Not all MySQL server versions or MySQLi client drivers support all properties.
If you need to set properties, use the mysqli_stmt::attr_set method, and you also need to first determine the support situation.
The mysqli_stmt::attr_get function can not only obtain the attribute value of the preprocessing statement, but also use it to determine whether certain attributes are supported. With this example, you can easily detect environment support and ensure that the program runs stably in different environments. It is recommended to add this judgment when writing complex applications that interact with the database to improve the robustness of the code.
