PHP生成的ZIP文件无法修改??求高手解释,为什么?
以下是生成zip类代码:<?php

# PHPZip v1.2 by Sext ([email protected]) 2002-11-18
#         (Changed: 2003-03-01)

# Makes zip archive
#
# Based on "Zip file creation class", uses zLib
#
# Examples in sample1.php, sample2.php and sample3.php
#class PHPZip
{
        function Zip($dir, $zipfilename)
        {
            if (@function_exists('gzcompress'))
                {        
                        $curdir = getcwd();
                        if (is_array($dir)) 
                        {
                                        $filelist = $dir;
                        }
                        else 
                        {
                                $filelist = $this -> GetFileList($dir);
                        }
                        
                        if ((!empty($dir))&&(!is_array($dir))&&(file_exists($dir))) chdir($dir);
                        else chdir($curdir);                        if (count($filelist)>0)
                        {
                                foreach($filelist as $filename)
                                {
                                        if (is_file($filename))
                                        {
                                                $fd = fopen ($filename, "r");
                                                $content = fread ($fd, filesize ($filename));
                                                fclose ($fd);                                                if (is_array($dir)) $filename = basename($filename);
                                                $this -> addFile($content, $filename);
                                        }
                                }
                                $out = $this -> file();                                chdir($curdir);
file_put_contents($zipfilename,$out);
                                //$fp = fopen($zipfilename, "w+");
                                //fwrite($fp, $out, strlen($out));
                                //fclose($fp);
                        }
                        return 1;
                } 
                else return 0;
        }        function GetFileList($dir)
        {
                if (file_exists($dir))
                {
                        $args = func_get_args();
                        $pref = $args[1];
           
                        $dh = opendir($dir);
                        while($files = readdir($dh))
                        {
                                if (($files!=".")&&($files!="..")) 
                                {
                                        if (is_dir($dir.$files)) 
                                        {
                                                $curdir = getcwd();
                                                chdir($dir.$files);
                                                $file = array_merge($file, $this -> GetFileList("", "$pref$files/"));
                                                chdir($curdir);
                                        }
                                        else $file[]=$pref.$files;
                                }
                        }
                        closedir($dh);
                }
                return $file;
        }    var $datasec      = array();
    var $ctrl_dir     = array();
    var $eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00";
    var $old_offset   = 0;    /**
     * Converts an Unix timestamp to a four byte DOS date and time format (date
     * in high two bytes, time in low two bytes allowing magnitude comparison).
     *
     * @param  integer  the current Unix timestamp
     *
     * @return integer  the current date in a four byte DOS format
     *
     * @access private
     */
    function unix2DosTime($unixtime = 0) {
        $timearray = ($unixtime == 0) ? getdate() : getdate($unixtime);        if ($timearray['year'] < 1980) {
                $timearray['year']    = 1980;
                $timearray['mon']     = 1;
                $timearray['mday']    = 1;
                $timearray['hours']   = 0;
                $timearray['minutes'] = 0;
                $timearray['seconds'] = 0;
        } // end if        return (($timearray['year'] - 1980) << 25) | ($timearray['mon'] << 21) | ($timearray['mday'] << 16) |
                ($timearray['hours'] << 11) | ($timearray['minutes'] << 5) | ($timearray['seconds'] >> 1);
    } // end of the 'unix2DosTime()' method
    /**
     * Adds "file" to archive
     *
     * @param  string   file contents
     * @param  string   name of the file in the archive (may contains the path)
     * @param  integer  the current timestamp
     *
     * @access public
     */
    function addFile($data, $name, $time = 0)
    {
        $name     = str_replace('\\', '/', $name);        $dtime    = dechex($this->unix2DosTime($time));
        $hexdtime = '\x' . $dtime[6] . $dtime[7]
                  . '\x' . $dtime[4] . $dtime[5]
                  . '\x' . $dtime[2] . $dtime[3]
                  . '\x' . $dtime[0] . $dtime[1];
        eval('$hexdtime = "' . $hexdtime . '";');        $fr   = "\x50\x4b\x03\x04";
        $fr   .= "\x14\x00";            // ver needed to extract
        $fr   .= "\x00\x00";            // gen purpose bit flag
        $fr   .= "\x08\x00";            // compression method
        $fr   .= $hexdtime;             // last mod time and date        // "local file header" segment
        $unc_len = strlen($data);
        $crc     = crc32($data);
        $zdata   = gzcompress($data);
        $c_len   = strlen($zdata);
        $zdata   = substr(substr($zdata, 0, strlen($zdata) - 4), 2); // fix crc bug
        $fr      .= pack('V', $crc);             // crc32
        $fr      .= pack('V', $c_len);           // compressed filesize
        $fr      .= pack('V', $unc_len);         // uncompressed filesize
        $fr      .= pack('v', strlen($name));    // length of filename
        $fr      .= pack('v', 0);                // extra field length
        $fr      .= $name;        // "file data" segment
        $fr .= $zdata;        // "data descriptor" segment (optional but necessary if archive is not
        // served as file)
        $fr .= pack('V', $crc);                 // crc32
        $fr .= pack('V', $c_len);               // compressed filesize
        $fr .= pack('V', $unc_len);             // uncompressed filesize        // add this entry to array
        $this -> datasec[] = $fr;
        $new_offset        = strlen(implode('', $this->datasec));        // now add to central directory record
        $cdrec = "\x50\x4b\x01\x02";
        $cdrec .= "\x00\x00";                // version made by
        $cdrec .= "\x14\x00";                // version needed to extract
        $cdrec .= "\x00\x00";                // gen purpose bit flag
        $cdrec .= "\x08\x00";                // compression method
        $cdrec .= $hexdtime;                 // last mod time & date
        $cdrec .= pack('V', $crc);           // crc32
        $cdrec .= pack('V', $c_len);         // compressed filesize
        $cdrec .= pack('V', $unc_len);       // uncompressed filesize
        $cdrec .= pack('v', strlen($name) ); // length of filename
        $cdrec .= pack('v', 0 );             // extra field length
        $cdrec .= pack('v', 0 );             // file comment length
        $cdrec .= pack('v', 0 );             // disk number start
        $cdrec .= pack('v', 0 );             // internal file attributes
        $cdrec .= pack('V', 32 );            // external file attributes - 'archive' bit set        $cdrec .= pack('V', $this -> old_offset ); // relative offset of local header
        $this -> old_offset = $new_offset;        $cdrec .= $name;        // optional extra field, file comment goes here
        // save to central directory
        $this -> ctrl_dir[] = $cdrec;
    } // end of the 'addFile()' method
    /**
     * Dumps out file
     *
     * @return  string  the zipped file
     *
     * @access public
     */
 function file()
    {
        $data    = implode('', $this -> datasec);
        $ctrldir = implode('', $this -> ctrl_dir);
//$comment='我就是注释啦,知道不?\n\n';
//$comment=file_get_contents("E:/说明.txt");
        return
            $data .
            $ctrldir .
            $this -> eof_ctrl_dir .
            pack('v', sizeof($this -> ctrl_dir)) .  // total # of entries "on this disk"
            pack('v', sizeof($this -> ctrl_dir)) .  // total # of entries overall
            pack('V', strlen($ctrldir)) .           // size of central dir
            pack('V', strlen($data)) .              // offset to start of central dir
            "AAAABBBB";                             // .zip file comment length
    } } // end of the 'PHPZip' class
?>
AAAABBBB是给zip添加的注释,但是只要这个注释存在,新生成的压缩文件就无法修改内容,比如手动修改注释,删除压缩包里的文件,都无法操作,winrar会报错。求大神解释原因。