Why I am getting Cannot pass parameter 2 by reference error when I am using bindParam with a constant value?

I’m using this code and I’m beyond frustration:

try {
    $dbh = new PDO('mysql:dbname=' . DB . ';host=' . HOST, USER, PASS);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $dbh->setAttribute(PDO::MYSQL_ATTR_INIT_COMMAND, "SET NAMES 'utf8'");
}
catch(PDOException $e)
{
    ...
}
$stmt = $dbh->prepare('INSERT INTO table(v1, v2, ...) VALUES(:v1, :v2, ...)');
$stmt->bindParam(':v1', PDO::PARAM_NULL); // --> Here's the problem

JavaScript
​x
 
try {    $dbh = new PDO('mysql:dbname=' . DB . ';host=' . HOST, USER, PASS);    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);    $dbh->setAttribute(PDO::MYSQL_ATTR_INIT_COMMAND, "SET NAMES 'utf8'");}catch(PDOException $e){    ...}$stmt = $dbh->prepare('INSERT INTO table(v1, v2, ...) VALUES(:v1, :v2, ...)');$stmt->bindParam(':v1', PDO::PARAM_NULL); // --> Here's the problem​

PDO::PARAM_NULL, null, '', all of them fail and throw this error:

Fatal error: Cannot pass parameter 2 by reference in /opt/…

Answer

You need to use bindValue, not bindParam

bindParam takes a variable by reference, and doesn’t pull in a value at the time of calling bindParam. I found this in a comment on the PHP docs:

bindValue(':param', null, PDO::PARAM_INT);

JavaScript
 
bindValue(':param', null, PDO::PARAM_INT);​

P.S. You may be tempted to do this bindValue(':param', null, PDO::PARAM_NULL); but it did not work for everybody (thank you Will Shaver for reporting.)

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Answer