Increment my variable in a database with UPDATE in PHP

Question

I get the variable 'stock' from my database. I would like increment my variable with an update with this code:

$stock = $_POST['stock']

$nom = 'salade';
$req=("UPDATE ingredients SET stock=$stock+1 WHERE nom = :nom;");
 $stmt = $db->prepare($req);

    // execute the query
    $stmt->execute(array('nom'=>$nom));

But the problem is that my variable increment by 8 and not by 1 because I have 8 element (salade,tomatoes, bread etc). I want to increment by 1 with UPDATE.

Thanks to reading me !

Answer 1

Considering that you're saying all you need to is increment by 1 each row WHERE nom = :nom (I guess your actual code isn't wrong with $ instead of : or it wouldn't even "increment by 8" as you said you're already achieving... remember do edit this on your question, please):

UPDATE
    ingredients
SET
    stock=stock+1
WHERE
    nom = :nom;

Jusk pick what you already had and add 1 stock=stock+1.

Answer 2

You can use like this for variable in text query.

$req= ("UPDATE ingredients SET stock='".($stock+1)."' WHERE nom = :nom;");