- substr: documentation ( source)
- str_replace: documentation ( source)
- strrpos: documentation ( source)
<?php
$file_name = "PL1134-38 VSD hangtag order form 9.25-.xls";
$ndot = strrpos($file_name,".");
$extension = substr($file_name,1,$ndot);
$prefix = $file_name.substr(0,$ndot);
$prefix = str_replace(".","",$prefix);
$file_name = $prefix + $extension;
echo $file_name;