kiểm tra link tên miền http + https

$str = $value['tk_website'];
$sub = "https://";
$sub2 = "http://";

if (strlen(strstr($str, $sub)) > 0) {
$url = $value['tk_website'];
} else {
if (strlen(strstr($str, $sub2)) > 0) {
$url = $value['tk_website'];
} else {
$url = "http://".$value['tk_website'];
}
}