What are the differences between bindParam() and bindValue() functions in PHP PDO statements, and when should each be used for optimal performance and error handling?

The main difference between bindParam() and bindValue() functions in PHP PDO statements is that bindParam() binds a parameter as a reference, while bindValue() binds a parameter as a value. bindParam() is useful when you want to pass a variable by reference and have its value updated during the execution of the statement, while bindValue() is more suitable for passing a specific value that should not be modified. Using bindParam() can be more efficient in terms of memory usage and performance when dealing with large datasets or when the same parameter needs to be bound multiple times with different values. On the other hand, bindValue() is simpler to use and can be more convenient for one-time bindings or when the parameter value should not change. Here is an example PHP code snippet that demonstrates the use of bindParam() and bindValue() functions:

// Using bindParam()
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = :id");
$id = 1;
$stmt->bindParam(':id', $id, PDO::PARAM_INT);
$stmt->execute();

// Using bindValue()
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$username = 'john_doe';
$stmt->bindValue(':username', $username, PDO::PARAM_STR);
$stmt->execute();