An example of code to determine uploaded file type in PHP

/**
 * Determine uploaded file type
 * Edit bbs.it-home.org
*/
    function file_type($filename)
    {
        $file = fopen($filename, "rb");
        $bin = fread($file, 2); //只读2字节
        fclose($file);
        $strInfo = @unpack("C2chars", $bin);
        $typeCode = intval($strInfo['chars1'].$strInfo['chars2']);
        $fileType = '';
        switch ($typeCode)
        {
            case 7790:
                $fileType = 'exe';
                break;
            case 7784:
                $fileType = 'midi';
                break;
            case 8297:
                $fileType = 'rar';
                break;
            case 8075:
                $fileType = 'zip';
                break;
            case 255216:
                $fileType = 'jpg';
                break;
            case 7173:
                $fileType = 'gif';
                break;
            case 6677:
                $fileType = 'bmp';
                break;
            case 13780:
                $fileType = 'png';
                break;
            default:
                $fileType = 'unknown: '.$typeCode;
        }

        //Fix
        if ($strInfo['chars1']=='-1' AND $strInfo['chars2']=='-40' ) return 'jpg';
        if ($strInfo['chars1']=='-119' AND $strInfo['chars2']=='80' ) return 'png';

        return $fileType;
    }

    //调用
    echo file_type('start.php');   // 6063 or 6033
?>

不知道反过来定义 6063或者6033 就是指php的话 是不是不够严谨啊。

上面的代码，对于构造假的图片的文件类型判断，不是很好使。 此时可以考虑使用getimagesize来判断，参考代码如下：

/**
 * getimagesize determines the file type
 * Edit bbs.it-home.org
*/
if(in_array($attach['ext'], array('jpg', 'jpeg', 'gif', 'png', 'swf', 'bmp')) && function_exists('getimagesize') && !@getimagesize($target))
{
  unlink($target);
  upload_error('post_attachment_ext_notallowed', $attacharray);
}
?>