Non-PHP version. Working with HTML. Be sure to change "accountName" to the username you use to sign into ERS.
Code:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script type="text/javascript">
var accountName = "REPLACE_THIS_WITH_YOUR_ACCOUNT_NAME";
$.get("https://everythingrs.com/api/players-online/get/" + accountName, function(response) {
$("#players").html(response);
});
</script>
There are currently <span id="players"></span> players online.
Not everyone uses paid webhosting, so that wouldn't have been an option for them unfortunately.