Loop in associative array with multiple fields in PHP

I've got a problem in my PHP code.

My original code was :

$listehoraires = $dbco->prepare("SELECT numero, horaire from `horaires`");
$listehoraires -> execute();

foreach ($listehoraires as $numero => $horaire) {
    $_SESSION['horaires'] += [$numero => $horaire]; 
}

Now, I need to select 3 fields in a database table :

$listehoraires = $dbco->prepare("SELECT numero, actif, horaire from `horaires`");
$listehoraires -> execute();

"actif" (=active) is used as a boolean to know if I add $numero and $horaire at the session variable and contains "yes" or "no".

I want to have something like :

foreach ($listehoraires as $numero => $horaire) {
     if ($actif == 'yes') $_SESSION['horaires'] += [$numero => $horaire]; 
}

but I don't know how to write it.

Any idea ?