Remove empty places in comma separated list with preg_replace

This is how you can remove empty places in a comma separated list e.g when you have a list like "one, , two, , three, , " and you want it to look like "one, two, three"

<?php
    $input = "one, , , two, ";
    //$input = ", two, two, ";
    //$input = ", two, two";
   
    $input = preg_replace( "/, , |, $|^, /", "", $input);

    echo $input;
?>
Knowledge keywords: 
regular expression
string
strings