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

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