value1, value2, value3, value4 etc...

$data["subscribers"];

/* Remove value from comma seperated string */
    function removeFromString($str, $item) {
    $parts = explode(',', $str);

    while(($i = array_search($item, $parts)) !== false) {
        unset($parts[$i]);
    }

    return implode(',', $parts);
    }
    $newString = removeFromString($existArr, $userdata["id"]);

function addtoString($str, $item) {
    $parts = explode(',', $str);
    $parts[] = $item;

    return implode(',', $parts);
    }
    $newString = addtoString($existArr, $userdata["id"]);

function addToString($str, $item) {
    $parts = explode(',', $str);
    array_push($parts, $str);
    return implode(',', $parts);
}
$newString = addToString($existArr, $userdata["id"]);

function addItem($str, $item) {
    return ($str != '' ? $str.',' : '').$item;
}