PHP如何根据文件头检测文件类型实例代码

前言

什么是文件头部Bom？ 说白了，就是在保存文件的时候，文件前面会多出一串隐藏的字符，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：

<?php
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：

<?php
/*通过文件名，获得文件类型*
 *@author chengmo QQ:8292669*
 *@copyright <a href="http://www.cnblogs.com/chengmo">http://www.cnblogs.com/chengmo</a> 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：

<?php
$filename = '22.jpg';

$extname = strtolower(substr($filename, strrpos($filename, '.') + 1));
echo $extname.'<br />';
$file = @fopen($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;

总结