Mysqli_stmt::bind_param and attr_get use order

When using the MySQLi extension of PHP for preprocessing statement operations, mysqli_stmt::bind_param is a very common method for binding parameters into preprocessing statements. On the other hand, mysqli_stmt::attr_get is used to get the properties of the preprocessing statement. Whether the order of call of these two methods will affect the result, and whether attr_get is required to call bind_param safely is a question that many developers are concerned about.

The role of mysqli_stmt::bind_param

The bind_param method is used to bind variables to parameter marks (question marks) in a preprocessing statement. The core function of this method is to implement parameterized queries to prevent SQL injection and improve execution efficiency. The basic usage is as follows:

 $stmt = $mysqli->prepare("SELECT * FROM users WHERE id = ?");
$id = 1;
$stmt->bind_param("i", $id);
$stmt->execute();

Here "i" means that the parameter type of the bound is an integer.

The role of mysqli_stmt::attr_get

attr_get is used to obtain the properties of preprocessing statements, such as MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH , etc. It is usually used for debugging or in some special cases to check the status of preprocessing statements.

For example:

 $max_length = $stmt->attr_get(MYSQLI_STMT_ATTR_UPDATE_MAX_LENGTH);
echo "Max length updated: " . $max_length;

Do you need to call attr_get first?

Normally, attr_get is not a necessary step to perform binding parameters. bind_param can be called directly, as long as the preprocessing statement has been prepared successfully, the binding parameter type and variable are correct.

The call order is recommended as follows:

1. $stmt = $mysqli->prepare($sql);

2. $stmt->bind_param($types, ...$vars);

3. $stmt->execute();

Calling attr_get is optional, mainly used to obtain attribute information, and has no direct dependency between binding parameters.

The effect of call order on the result

• Call attr_get first and then bind_param :
  This does not affect the execution of bind_param , provided that the preprocessing statement is ready. attr_get just gets the attribute and will not modify the status of the bound parameters.

• Call bind_param first and then attr_get :
  This will not affect the value of the attr_get obtaining attributes, and the order of call has no effect on the function.

In summary, there is no strict call order dependency between attr_get and bind_param , both are independent of each other, and attr_get is usually an optional operation.

Sample code