PHP replace char with Unicode value inside string

<?php
$originalString = "Pritom K Mondal, 0154785";
function ord2($s2) {
    return "&#" . ord($s2) . ";";
}
echo preg_replace("/[^a-zA-Z0-9]/e", "ord2('\\0')", $originalString) ?>

And output will be as:

Pritom K Mondal, 0154785