<?php
function insertInPosition($str, $pos, $c){
}
$str = "30000000";
echo insertInPosition($str, 4, '.');
PD9waHAKZnVuY3Rpb24gaW5zZXJ0SW5Qb3NpdGlvbigkc3RyLCAkcG9zLCAkYyl7CiAgICByZXR1cm4gc3Vic3RyKCRzdHIsIDAsICRwb3MpIC4gJGMgLiBzdWJzdHIoJHN0ciwgJHBvcyk7Cn0KCiRzdHIgPSAiMzAwMDAwMDAiOwplY2hvIGluc2VydEluUG9zaXRpb24oJHN0ciwgNCwgJy4nKTs=