<?php
    function getFileSize($file_name){
        $K = 1024;
        $M = 1024*$K;
        $G = 1024*$M;
        $file_size = filesize($file_name);
        if($file_size>$G){
            $file_size = ($file_size / $G)." G";
        }elseif($file_size>$M){
            $file_size = ($file_size / $M) ." M";
        }elseif($file_size > $K){
            $file_size = ($file_size /$K). " K";
        }else{
            $file_size = $file_size. " byte";
        }
        return $file_size;
    }
    echo getFileSize("new_file.html");
?>