使用PHP PDO和MySql时绑定IS NULL或NULL

Question

How can I bind NULL in the following scenario. No matter what I do, I can't get it to work.

if ($type == 1) {
    $self   = 'NULL';
    $parent = 'NULL';
}

$findThis = $conn->prepare('select count(id) as exists from table where id = :id and self = :self and parent = :parent';

$findThis->execute(array(
    ":id"     => $id,
    ":self"   => $self,
    ":parent" => $parent
));

Answer 1

For null values, you have to use IS NULL in the sql instead.