Php how to remove any last commas

Question

Example output

1. test,test,test,test,test,
2. test,test,test,,
3. test,test,,,
4. test,,,,,

I tried use implode according to my previous q

Answer 1

completely different way:

$str = "1,2,3,4,";
$str = substr($str,0,strlen($str)-1);