Using PDO Prepared Statement and Incrementing a column value

Question

I\'ve read this thread: Issues incrementing a field in MySQL/PHP with prepared statements but didn\'t see the answer to my problem.

PDOStatement Object
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Answer 1

Using parameters is not just a simple text replacement. You can't replace a column name with a parameter. MySQL will interpret your query as if you had written this:

UPDATE user_alerts SET notif = 'notif' + 2 WHERE ( user_id = ? ) 

The string 'notif' is converted to zero for the addition.

Try this query instead:

UPDATE user_alerts SET notif = notif + 2 WHERE ( user_id = ? )   

Answer 2

$sql = 'UPDATE user_alerts SET notif = notif + 2 WHERE ( user_id = :userid )';
$prepStatement = $pdo->prepare( $sql );
$prepStatement->execute(array(':userid' => $userid));

You can't bind a column name to a prepared statement.