Chrome操纵Javascript参数？

Long story short: I'm doing a project that looks for database entries containing your Steam ID after loggin in via Steam's OpenID.

I get the Steam ID with PHP, which works quite well (I get the correct id). After getting the ID I'm converting it via a JavaScript to another kind of ID. This also works..basically.

Now it's getting strange. If I enter the Steam ID with a input field and let JavaScript convert it, everything's fine. But it doesn't work using the Steam login. The login gets the right id (tested with an echo line), but when I give the id as parameter to the JavaScript it's actually the ID + 10 and I have no clue why. Interestingly this only happens in Chrome and Firefox, Microsoft Edge does everything correct, but Chrome and Firefox are highering the ID by 10.

PHP:

if(!isset($_GET['steamID']) && !isset($_GET['armaID'])) {
    $steamID = SteamSignIn::validate();
    //Steam ID is correct here
    echo "<script>
    forwardSteamLogin(".$steamID.");
    </script>";
    //Steam ID still correct afterwards
    return;
}

JS:

function forwardSteamLogin(uid) {
    //UID / SteamID magically increased by 10 in FF and Chrome, but still correct in Edge
    var guid = getUid(uid);
    var urlToDirect = "?steamID="+uid+"&armaID="+guid;
    window.location.href = urlToDirect;
}

The solution was to pass the ID as String, I just forgot to set the quotation marks:

if(!isset($_GET['steamID']) && !isset($_GET['armaID'])) {
    $steamID = SteamSignIn::validate();
    echo '<script language="JavaScript">
                forwardSteamLogin("'.$steamID.'");
            </script>';
    return;
}

Thanks to @FelixKling for this.