PHP取二进制文件头快速判断文件类型

<?php
/*文件扩展名说明
  *7173         gif
  *255216       jpg
  *13780        png
  *6677         bmp
  *239187       txt,aspx,asp,sql
  *208207       xls.doc.ppt
  *6063         xml
  *6033         htm,html
  *4742         js
  *8075         xlsx,zip,pptx,mmap,zip
  *8297         rar  
  *01           accdb,mdb
  *7790         exe,dll          
  *5666         psd
  *255254       rdp
  *10056        bt种子
  *64101        bat
 */

    /*PHP取二进制文件头快速判断文件类型*/
    $files = array(
        'c:\1.jpg',
        'c:\1.png',
        'c:\1.gif',
        'c:\1.rar',
        'c:\1.zip',
        'c:\1.exe',
    );

    foreach ($files AS $file) {
        $fp = fopen($file, "rb");
        $bin = fread($fp, 2); //只读2字节
        fclose($fp);
        $str_info  = @unpack("C2chars", $bin);
        $type_code = intval($str_info['chars1'].$str_info['chars2']);
        $file_type = '';
        switch ($type_code) {
            case 7790:
                $file_type = 'exe';
                break;
            case 7784:
                $file_type = 'midi';
                break;
            case 8075:
                $file_type = 'zip';
                break;
            case 8297:
                $file_type = 'rar';
                break;
            case 255216:
                $file_type = 'jpg';
                break;
            case 7173:
                $file_type = 'gif';
                break;
            case 6677:
                $file_type = 'bmp';
                break;
            case 13780:
                $file_type = 'png';
                break;
            default:
                $file_type = 'unknown';
                break;
        }

        echo $file , ' type: <b>', $file_type, '</b> code:<b>', $type_code, '</b><br />';

    }