อัพโหลดไฟล์ภาษาไทย โดยเข้ารหัส ด้วยฟังก์ชัน md5() และให้ถอดรหัส ก่อนดาวน์โหลด นี่ ผมไม่เข้าใจสักเลย งง ช่วยหน่อยครับ

<meta http-equiv="content-type" content="text/html; charset=utf-8" />

<style>
body {
background: url('images/bg.jpg') top center ;
background-attachment:fixed;
background-size: 100%;
background-origin: content;
background-repeat: no-repeat;
}
</style>
<?php 
include "class.resizepic.php";
$db = new mysqli("localhost", "root", "123456", "dbboard");
$db->set_charset('utf8');

if(isset($_POST['Submit'] ))
{
	$num_file = count($_FILES['file']['name']);
	$select = false;
	$count = 0;
	for($i = 0; $i < $num_file ; $i++)
	{
		if($_FILES['file']['error'][$i] != 0) 
		{
		    $count++;
			continue;
		}
		if($_FILES['file']['name'][$i] != "")
		{
			
			#ฟังก์ชั่นนี้ใช้สำหรับ Rename ชื่อไฟล์ที่ทำการอัพโหลดใหม่ รับค่า $_FILES['file']['name']
			#ผลลัพธิ์จะได้ เช่น รับค่า ทดสอบ.docx ฟังก์ชั่นจะส่งค่ามาเป็น Acdeq12345678.docx เป็นต้น
			function getNewName($fileName){
				$fileName = explode('.',$fileName);
				$i = count($fileName)-1;
				$fileType = strtolower($fileName[$i]);
				$rand = substr(str_shuffle('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ123456789'),0,5);
				$result = $rand.time().'.'.$fileType;
				return $result;
			}
			
			$Filename = getNewName($_FILES['file']['name'][$i]);
			$originalFilename = $_FILES['file']['name'][$i];
			$type = $_FILES['file']['type'][$i];
			
			// .gif, .png, .jpg, .zip, .docx, .pdf, .doc, .swf, .rar
			if ( $type == "image/gif") {$pic_type = 'GIF'; }
			else if ($type == "image/png") {$pic_type = 'PNG'; }
			else if (($type == "image/jpg") or ($type=="image/jpeg") or ($type == "image/pjpeg")) {$pic_type = 'JPG'; }
			else if ($type == "application/octet-stream") {$pic_type = false;}
			else if ($type == "application/vnd.openxmlformats-officedocument.wordprocessingml.document") {$pic_type = false;}
			else if ($type == "application/pdf") {$pic_type = false;}
			else if ($type == "application/msword") {$pic_type = false;}
			else if ($type == "application/x-shockwave-flash") {$pic_type = false;}
			else if ($type == "application/octet-stream") {$pic_type = false;}
			
			
	
			if(move_uploaded_file($_FILES['file']['tmp_name'][$i], "fileUpload/".$Filename)){
			
			if($pic_type){
					$original_image = "fileUpload/". $Filename ; 
					$pic_size = getimagesize($original_image);
					$desired_width = 250 ;
					$per_div = abs($desired_width - $pic_size[0]) * 100 / $pic_size[0];
					$desired_height = $pic_size[0] > $desired_width ?  $pic_size[1] - floor( $pic_size[1] * $per_div / 100) : $pic_size[1] + floor( $pic_size[1] * $per_div / 100);
					$image = new hft_image($original_image);
					$image->resize($desired_width, $desired_height, '0');
					$image->output_resized("fileUpload/".$Filename, "JPG");
				}
				
						$sql = $db->query("INSERT INTO files (original_file_name , file_name) VALUES ('{$originalFilename}' , '{$Filename}') ");
				if($sql)
				{
			 		echo "<H3><CENTER><br><br><br><br><br><img src='images/thumbsup.png' width='256px' height='161px'></CENTER></H3>";
			 		echo "<META HTTP-EQUIV=refresh CONTENT=\"0; page_admin.php\">";
					$upload_true = true;
			 	}else{
			 		echo "<H3>ERROR:Can not Upload</H3>";
				 }
			}
		}else{
			$count++;
		}
	}
}
?>