使用PDO绑定SOMETIMES null值

Question

There is only one record in my database, and the "action_taken" column is set to NULL. How the hell do I get PDO to find it???

If I type the query directly into SQL it works as expected.

Note: This is just a test script to illustrate my problem. Most the time the value passed will be a string, but occasionally the value will be NULL.

include ('include/mysql.php');

$sql = 'SELECT * FROM returns WHERE action_taken = :action';
$sth = $dbh->prepare($sql);
$param = null;
$sth->bindValue(':action', $param, PDO::PARAM_STR);
$sth->execute();
if ($sth->rowCount())
    {
    echo 'FOUND YOU!';
    }
else
    {
    echo 'NOOOO :(';
    }

Answer 1

Basically, you can't say "equal to null". It always has to be IS null:

$sql = 'SELECT * FROM returns WHERE action_taken IS :action';

You'd be better off not using NULL at all, if at all possible.