在php PDO中无法通过引用错误传递参数2

Question

I am getting the error: Cannot pass parameter 2 by reference in.....

in this line...

$stmt1->bindParam(':value', $_SESSION['quantity'.$i] * $_SESSION['price'.$i], PDO::PARAM_STR);   

What is wrong with code above ??

Answer 1

It expects the second paramter to be a variable which can be passed by reference. Assuming $stmt1is a PDO statement then, as the docs for bindparam say

Unlike PDOStatement::bindValue(), the variable is bound as a reference and will only be evaluated at the time that PDOStatement::execute() is called.

Your second param is an expression ($_SESSION['quantity'.$i] * $_SESSION['price'.$i]) not a variable. Since you appear to want to evaluate the exptression now, I guess you should used bindValue() instead.