<?php

$size= ini_get("post_max_size"); //8M
      $letter = $size{strlen($size)-1}; //M
      $size = (int)$size; //8
      
      switch($letter){
          case "G" : $size *= 1024;
          case "M" : $size *= 1024;
          case "K" : $size *= 1024;  
      }
      echo $size;