PHP - how to store password_hash results in an array?

Question

I would like to hash multiple passwords from a MySQL table.

$oConnexion = mysqli_connect();
$req1 = <<<SQL
    SELECT TX_PASSWORD_USR
    FROM sc_t_utilisateur as u
SQL;
$oRs1 = mysqli_query($req1, $oConnexion);

$passwords = [];
while($fetch = mysqli_fetch_assoc($oRs1)){
    $passwords[] = $fetch['TX_PASSWORD_USR'];
}

$hashes = [];
foreach ($passwords as $password){
    $hashes[] = password_hash($password, PASSWORD_ARGON2ID, ["cost" => 13]);
}
var_dump($hashes);

It is OK to var_dump every password_hash but when I try to store the password_hash results in an array, nothing happened...