mysql - Using pdo in php with stored procedure

Question

I have a simple stored procedure in MySQL database:

DELIMITER $$
CREATE DEFINER=`vidhu`@`%` PROCEDURE `test`(var_datain TEXT)
BEGIN
    SELECT var_datain;
END

When calling this procedure in mysql-workbench it returns the data I put in:

Now when I call it from PHP using pdo I get an error:

Fatal error: Cannot pass parameter 2 by reference in C:/apache......(3rd line)

Here is my php code:

$db = new PDO(DSN, DBUSER, DBPASS);
$stmt = $db->prepare("CALL test(?)");
$stmt->bindParam(1, 'hai!', PDO::PARAM_STR);
$rs = $stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
echo $result[0];

Answer 1

You need to use bindValue instead of bindParam.

When you use bindParam, it binds the variable provided to the parameter, not the value of the variable.

So, if you do:

$x = 5;
$stmt->bindParam(1, $x, PDO::PARAM_INT);
$x = 6;
$stmt->execute(); //executes with 6 instead of 5

It's actually executed with 6 rather than 5. To do this, the method must have a reference to the variable. You cannot have a reference to a literal, so this means that bindParam cannot be used with literals (or anything you can't have a reference to).

$x = 5;
$stmt->bindValue(1, $x, PDO::PARAM_INT);
$x = 6;
$stmt->execute(); //executes with 5 instead of 6

Then:

$stmt->bindParam(1, 1, PDO::PARAM_INT); 
//invalid because there's no way to pass a literal 1 by reference
$stmt->bindValue(1, 1, PDO::PARAM_INT);
//valid