bindparam

BindParam is a method of PHP's PDOStatement class used to bind a parameter in a prepared SQL statement to a PHP variable by reference. The binding persists until the statement is executed, allowing the actual value to be supplied at execution time rather than when the binding is defined.

Parameters can be named placeholders (for example :name) or question marks ?. The first argument identifies the placeholder, the second is the variable to bind (passed by reference), and the optional third argument specifies the explicit data type (such as PDO::PARAM_INT or PDO::PARAM_STR). The method returns a boolean indicating success.

Binding by reference means that the value assigned to the variable is read at the moment execute() is called, not at bindParam() time. Consequently, changing the variable after binding but before executing will change the bound value. If you want to bind a value immediately, use bindValue instead.

Example:

$stmt = $pdo->prepare("SELECT * FROM users WHERE id = :id");

$id = 42;

$stmt->bindParam(':id', $id, PDO::PARAM_INT);

$stmt->execute();

$result = $stmt->fetchAll();

Notes: BindParam binds only to placeholders in the prepared statement; parameters can be re-bound before execute. The length parameter is supported for certain data types, and handling for large objects (LOBs) may require additional considerations. If placeholders are unnamed, you can bind by position using ?, referring to the parameters by index (1, 2, etc.). Related concepts include bindValue, execute with an array of values, and the broader use of prepared statements with PDO.