文件签名一般都在文件的头部，如果你用十六进制方式查看文件，你就可以看到文件的一些签名信息。如用uestudio以十六进制方式查看zip格式的文件，其文件内容头部有50 4B 03 04这样的十六进制信息。同理jpg文件状况有FF D8 FF E0 xx xx 4A 46这样的十六进制信息，其实这此十六进制都是表示一些特殊字条。
php怎么样验证文件类型？先来看一个简单的方法：
function checkFileType($fileName){
$file = fopen($fileName, "rb");
$bin = fread($file, 2); //只读2字节
fclose($file);
// C为无符号整数，网上搜到的都是c，为有符号整数，这样会产生负数判断不正常
$strInfo = @unpack("C2chars", $bin);
$typeCode = intval($strInfo['chars1'].$strInfo['chars2']);
$fileType = '';
switch( $typeCode )
{
case '255216':
return $typeCode. ' : ' .'jpg';
break;
case '7173':
return $typeCode. ' : ' .'gif';
break;
case '13780':
return $typeCode. ' : ' .'png';
break;
case '6677':
return $typeCode. ' : ' .'bmp';
break;
case '7790':
return $typeCode. ' : ' .'exe';
break;
case '7784':
return $typeCode. ' : ' .'midi';
break;
case '8297':
return $typeCode. ' : ' .'rar';
break;
default:
return $typeCode. ' : ' .'Unknown';
break;
}
//return $typeCode;
}
$file_name = '11.doc';
echo checkFileType($file_name);
下来提供一个类的实现：
/*通过文件名，获得文件类型*
*@author chengmo QQ:8292669*
*@copyright http://www.cnblogs.com/chengmo 2010-10-17
*@version 0.1
*$filename="d:/1.png";echo cFileTypeCheck::getFileType($filename); 打印：png
*/
class cFileTypeCheck
{
private static $_TypeList=array();
private static $CheckClass=null;
private function __construct($filename)
{
self::$_TypeList=$this->getTypeList();
}
/**
*处理文件类型映射关系表*
*
* @param string $filename 文件类型
* @return string 文件类型，没有找到返回：other
*/
private function _getFileType($filename)
{
$filetype="other";
if(!file_exists($filename)) throw new Exception("no found file!");
$file = @fopen($filename,"rb");
if(!$file) throw new Exception("file refuse!");
$bin = fread($file, 15); //只读15字节 各个不同文件类型，头信息不一样。
fclose($file);
$typelist=self::$_TypeList;
foreach ($typelist as $v)
{
$blen=strlen(pack("H*",$v[0])); //得到文件头标记字节数
$tbin=substr($bin,0,intval($blen)); ///需要比较文件头长度
if(strtolower($v[0])==strtolower(array_shift(unpack("H*",$tbin))))
{
return $v[1];
}
}
return $filetype;
}
/**
*得到文件头与文件类型映射表*
*
* @return array array(array('key',value)...)
*/
public function getTypeList()
{
return array(array("FFD8FFE1","jpg"),
array("89504E47","png"),
array("47494638","gif"),
array("49492A00","tif"),
array("424D","bmp"),
array("41433130","dwg"),
array("38425053","psd"),
array("7B5C727466","rtf"),
array("3C3F786D6C","xml"),
array("68746D6C3E","html"),
array("44656C69766572792D646174","eml"),
array("CFAD12FEC5FD746F","dbx"),
array("2142444E","pst"),
array("D0CF11E0","xls/doc"),
array("5374616E64617264204A","mdb"),
array("FF575043","wpd"),
array("252150532D41646F6265","eps/ps"),
array("255044462D312E","pdf"),
array("E3828596","pwl"),
array("504B0304","zip"),
array("52617221","rar"),
array("57415645","wav"),
array("41564920","avi"),
array("2E7261FD","ram"),
array("2E524D46","rm"),
array("000001BA","mpg"),
array("000001B3","mpg"),
array("6D6F6F76","mov"),
array("3026B2758E66CF11","asf"),
array("4D546864","mid"));
}
public static function getFileType($filename)
{
if(!self::$CheckClass) self::$CheckClass=new self($filename);
$class=self::$CheckClass;
return $class->_getFileType($filename);
}
}
$filename="22.jpg";
echo $filename,"t",cFileTypeCheck::getFileType($filename),"rn";
$filename="11.doc";
echo $filename,"t",cFileTypeCheck::getFileType($filename),"rn";
或者可以这么检测：
$filename = '22.jpg'; $extname = strtolower(substr($filename, strrpos($filename, '.') + 1)); echo $extname.'
'; $file = @fopen($filename, 'rb'); if ($file) { $str = @fread($file, 0x400); // 读取前 1024 个字节 echo substr($str, 0, 4); @fclose($file); } if (substr($str, 0, 4) == 'MThd' && $extname != 'txt') { $format = 'mid'; } elseif (substr($str, 0, 4) == 'RIFF' && $extname == 'wav') { $format = 'wav'; } elseif (substr($str ,0, 3) == "/xFF/xD8/xFF") { $format = 'jpg'; } elseif (substr($str ,0, 4) == 'GIF8' && $extname != 'txt') { $format = 'gif'; } elseif (substr($str ,0, 8 ) == "/x89/x50/x4E/x47/x0D/x0A/x1A/x0A") { $format = 'png'; } elseif (substr($str ,0, 2) == 'BM' && $extname != 'txt') { $format = 'bmp'; } elseif ((substr($str ,0, 3) == 'CWS' || substr($str ,0, 3) == 'FWS') && $extname != 'txt') { $format = 'swf'; } elseif (substr($str ,0, 4) == "/xD0/xCF/x11/xE0") { // D0CF11E == DOCFILE == Microsoft Office Document if (substr($str,0x200,4) == "/xEC/xA5/xC1/x00" || $extname == 'doc') { $format = 'doc'; } elseif (substr($str,0x200,2) == "/x09/x08" || $extname == 'xls') { $format = 'xls'; } elseif (substr($str,0x200,4) == "/xFD/xFF/xFF/xFF" || $extname == 'ppt') { $format = 'ppt'; } } elseif (substr($str ,0, 4) == "PK/x03/x04") { $format = 'zip'; } elseif (substr($str ,0, 4) == 'Rar!' && $extname != 'txt') { $format = 'rar'; } elseif (substr($str ,0, 4) == "/x25PDF") { $format = 'pdf'; } elseif (substr($str ,0, 3) == "/x30/x82/x0A") { $format = 'cert'; } elseif (substr($str ,0, 4) == 'ITSF' && $extname != 'txt') { $format = 'chm'; } elseif (substr($str ,0, 4) == "/x2ERMF") { $format = 'rm'; } elseif ($extname == 'sql') { $format = 'sql'; } elseif ($extname == 'txt') { $format = 'txt'; } echo $format;
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