php multi base programming practice for detecting picture trojans

Not long ago, I applied to join an open source organization and they asked me to write a function to check if there is a Trojan script in the picture.
In fact, I did not know anything at the beginning of 1, but later looked up some information on the Internet, found all have made a picture of the Trojan tutorial, and did not find the detection process.

After a few thoughts, decided to make from the principle of the Trojan program to analyze. This trojans program is written in base 106 code, I was inspired to move 1, wrote the following upload class. Finally passed the organization test. Ha ha

Now take it out to share with everyone, what is not good, please correct! anyon@139.com;

 
<?php 
/** 
+------------------------------------------------------------------------------ 
* Upload  File upload class  
+------------------------------------------------------------------------------ 
* @package Upload 
* @author Anyon <Anyon@139.com> 
* @version $Id: Upload.class.php 2013-3-20 21:47:23 Anyon $ 
+------------------------------------------------------------------------------ 
*/ 
class Upload { 
private static $image = null; 
private static $status = 0; 
private static $suffix = null; 
private static $imageType = array('.jpg', '.bmp','.gif','.png'); 
private static $message = array( 
'0' => ' No error occurred and the file was uploaded successfully. ', 
'1' => ' More files have been uploaded  php.ini  In the  upload_max_filesize  The value of the option limit. ', 
'2' => ' The size of the uploaded file is over  HTML  In the form  MAX_FILE_SIZE  The value specified by the option. ', 
'3' => ' Only part of the file is uploaded. ', 
'4' => ' No file uploaded. ', 
'5' => ' Documents that failed the security check. ', 
'6' => ' The temporary folder could not be found. ', 
'7' => ' File write failed. ', 
'8' => ' File types are not supported ', 
'9' => ' The uploaded temporary file is missing. ', 
); 
//@  Start the file upload  
public static function start($feild = 'file') { 
if (!empty($_FILES)) { 
self::$status = $_FILES[$feild]['error']; 
if (self::$status > 0) 
return array('status' => self::$status, 'msg' => self::$message[self::$status]); 
self::$image = $_FILES[$feild]['tmp_name']; 
self::$suffix = strtolower(strrchr($_FILES[$feild]['name'], '.')); 
return array('status' => self::_upload(), 'path' => self::$image, 'msg' => self::$message[self::$status]); 
} else { 
return array('status' => self::$status, 'msg' => self::$message[self::$status]); 
} 
} 
//@  private   Upload begins  
private static function _upload($path = './upload/') { 
date_default_timezone_set('PRC'); 
$newFile = $path . date('Y/m/d/His') . rand(100, 999) . self::$suffix; 
self::umkdir(dirname($newFile)); 
if (is_uploaded_file(self::$image) && move_uploaded_file(self::$image, $newFile)) { 
self::$image = $newFile; 
if (in_array(self::$suffix, self::$imageType)) 
return self::checkHex(); 
else 
return self::$status = 0; 
} else { 
return self::$status = 9; 
} 
} 
//@  private  16 In system testing  
private static function checkHex() { 
if (file_exists(self::$image)) { 
$resource = fopen(self::$image, 'rb'); 
$fileSize = filesize(self::$image); 
fseek($resource, 0); 
if ($fileSize > 512) { //  Take a head and tail  
$hexCode = bin2hex(fread($resource, 512)); 
fseek($resource, $fileSize - 512); 
$hexCode .= bin2hex(fread($resource, 512)); 
} else { //  Take all  
$hexCode = bin2hex(fread($resource, $fileSize)); 
} 
fclose($resource); 
/*  matching 16 In the base  <% ( ) %> */ 
/*  matching 16 In the base  <? ( ) ?> */ 
/*  matching 16 In the base  <script | /script>  Case may also */ 
if (preg_match("/(3c25.*?28.*?29.*?253e)|(3c3f.*?28.*?29.*?3f3e)|(3C534352495054)|(2F5343524950543E)|(3C736372697074)|(2F7363726970743E)/is", $hexCode)) 
self::$status = 5; 
else 
self::$status = 0; 
return self::$status; 
} else { 
return self::$status = 9; 
} 
} 
//@  private   Create a directory  
private static function umkdir($dir) { 
if (!file_exists($dir) && !is_dir($dir)) { 
self::umkdir(dirname($dir)); 
@mkdir($dir); 
} 
} 
}