PHP mysql PDO refuses to set NULL value

I will strong recommend to first assign all parameters to variables and then pass those variables to the bindParam() method.

You can assign by passing NULL to those variables and it will work fine.

$myVar = NULL;
$conn->bindParam(':param1' , $myVar , PDO::PARAM_STR);

The following works for me:

<?php

$pdo = new PDO("mysql:host=localhost;dbname=test", "root", "pass");
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

$stmt = $pdo->prepare("INSERT INTO `null_test` (`can_be_null`) VALUES (:null)");
$stmt->bindValue(":null", null, PDO::PARAM_NULL);

$stmt->execute();

Pass in PHP's null, with type of PDO::PARAM_NULL. Also, make sure your prepare emulation is set to false. That might help.