How to use php to generate zip compressed files with detailed code

require_once "./include/zip.php"; 
$zip = new PHPZip(); //
$zip -> createZip("要压缩的文件夹目录地址", "压缩后的文件名.zip");　　 //只生成不自动下载 $zip -> downloadZip("要压缩的文件夹目录地址", "压缩后的文件名.zip");　　//自动下载

require_once "./include/zip.php"; 
if (!$download) { 
exit(); 
} 
set_time_limit(60); 
$tmpManager = new TmpManager(); //假设我们有一个类来完成后面的操作 
$tempfolder = array(); 
$tempfile = array(); 
//假设我们是通过在页面上选择checkbox来下载已选的文件夹或文件，并一同打包 
for($i = 0;$i < $checkboxnum;$i++) { 
$value = ${"select".$i}; 
if ($value != &#39;&#39;) { 
$this_type = substr($value, 0, 1); 
$this_id = substr($value, 1); 
//将文件夹和文件的情况分开处理 
if ($this_type == &#39;d&#39;) { 
$tempfolder[] = $this_id; 
} 
elseif ($this_type == &#39;f&#39;) { 
$tempfile[] = $this_id; 
} 
} 
} 
@mkdir($tempdir); 
$curtempdir = "$tempdir/".$userid; //不同用户在不同的临时文件夹下操作 
if (file_exists($curtempdir)) { 
$tmpManager->DeleteDir($curtempdir); //删除旧的文件夹 
} 
if (sizeof($tempfolder) > 0 || sizeof($tempfile) > 0) { 
mkdir($curtempdir, 0777); //如果有要打包的文件货文件夹，重新创建文件夹 
} 
if (sizeof($tempfile) > 0) { 
$tmpManager->CopyFile($tempfile,$curtempdir); //将要下载的文件copy到创建的文件夹 
} 
if (sizeof($tempfolder) > 0) { 
$tmpManager->CopyFolder($tempfolder,$curtempdir); //将要下载的文件夹copy到创建的文件夹 
} 
$zip = new PHPZip(); 
$zip -> downloadZip($curtempdir, "file_".date(&#39;Ymd&#39;).".zip"); //打包并下载

<?php 
/* 
File name: /include/zip.php 
Author: Horace 2009/04/15 
*/ 
class PHPZip{ 
var $dirInfo = array("0","0"); 
var $rootDir = &#39;&#39;; 
var $datasec = array(); 
var $ctrl_dir = array(); 
var $eof_ctrl_dir = "/x50/x4b/x05/x06/x00/x00/x00/x00"; 
var $old_offset = 0; 
function downloadZip(){ 
createZip($dir, $zipfilename, true); 
} 
function createZip($dir, $zipfilename, $autoDownload = false){ 
if (@function_exists(&#39;gzcompress&#39;)){ 
@set_time_limit("0"); 
if (is_array($dir)){ 
$fd = fopen ($dir, "r"); 
$fileValue = fread ($fd, filesize ($filename)); 
fclose ($fd); 
if (is_array($dir)) $filename = basename($dir); 
$this -> addFile($fileValue, "$filename"); 
}else{ 
$this->dirTree($dir,$dir); 
} 
$zipfilenametemp = time().$zipfilename; 
$out = $this -> filezip(); 
$fp = fopen($zipfilenametemp, "w"); 
fwrite($fp, $out, strlen($out)); 
fclose($fp); 
$filesize = filesize($zipfilenametemp); 
if ($filesize < 104857600) { 
if($autoDownload){ 
header("Content-type: application/octet-stream"); 
header("Content-disposition: attachment; filename=".$zipfilename); 
} 
echo $this -> filezip(); 
}else{ 
echo "create zip error!"; 
} 
unlink($zipfilenametemp); 
} 
} 
//get dir tree.. 
function dirTree($directory,$rootDir){ 
global $_SERVER,$dirInfo,$rootDir; 
$fileDir=$rootDir; 
$myDir=dir($directory); 
while($file=$myDir->read()){ 
if(is_dir("$directory/$file") and $file!="." and $file!=".."){ 
$dirInfo[0]++; 
$rootDir ="$fileDir$file/"; 
$this -> addFile(&#39;&#39;, "$rootDir"); 
//go on n&#39;s folders 
$this->dirTree("$directory/$file",$rootDir); 
}else{ 
if($file!="." and $file!=".."){ 
$dirInfo[1]++; 
//$fd = fopen ("$directory/$file", "r"); 
$fileValue = file_get_contents("$directory/$file"); 
//fclose ($fd); 
$this -> addFile($fileValue, "$fileDir$file"); 
} 
} 
} 
$myDir->close(); 
} 
function unix2DosTime($unixtime = 0) { 
$timearray = ($unixtime == 0) ? getdate() : getdate($unixtime); 
if ($timearray[&#39;year&#39;] < 1980) { 
$timearray[&#39;year&#39;] = 1980; 
$timearray[&#39;mon&#39;] = 1; 
$timearray[&#39;mday&#39;] = 1; 
$timearray[&#39;hours&#39;] = 0; 
$timearray[&#39;minutes&#39;] = 0; 
$timearray[&#39;seconds&#39;] = 0; 
} // end if 
return (($timearray[&#39;year&#39;] - 1980) << 25) | ($timearray[&#39;mon&#39;] << 21) | ($timearray[&#39;mday&#39;] << 16) | 
($timearray[&#39;hours&#39;] << 11) | ($timearray[&#39;minutes&#39;] << 5) | ($timearray[&#39;seconds&#39;] >> 1); 
} 
function addFile($data, $name, $time = 0){ 
$name = str_replace(&#39;//&#39;, &#39;/&#39;, $name); 
$dtime = dechex($this->unix2DosTime($time)); 
$hexdtime = &#39;/x&#39; . $dtime[6] . $dtime[7] 
. &#39;/x&#39; . $dtime[4] . $dtime[5] 
. &#39;/x&#39; . $dtime[2] . $dtime[3] 
. &#39;/x&#39; . $dtime[0] . $dtime[1]; 
eval(&#39;$hexdtime = "&#39; . $hexdtime . &#39;";&#39;); 
$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(&#39;V&#39;, $crc); // crc32 
$fr .= pack(&#39;V&#39;, $c_len); // compressed filesize 
$fr .= pack(&#39;V&#39;, $unc_len); // uncompressed filesize 
$fr .= pack(&#39;v&#39;, strlen($name)); // length of filename 
$fr .= pack(&#39;v&#39;, 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(&#39;V&#39;, $crc); // crc32 
$fr .= pack(&#39;V&#39;, $c_len); // compressed filesize 
$fr .= pack(&#39;V&#39;, $unc_len); // uncompressed filesize 
// add this entry to array 
$this -> datasec[] = $fr; 
$new_offset = strlen(implode(&#39;&#39;, $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(&#39;V&#39;, $crc); // crc32 
$cdrec .= pack(&#39;V&#39;, $c_len); // compressed filesize 
$cdrec .= pack(&#39;V&#39;, $unc_len); // uncompressed filesize 
$cdrec .= pack(&#39;v&#39;, strlen($name) ); // length of filename 
$cdrec .= pack(&#39;v&#39;, 0 ); // extra field length 
$cdrec .= pack(&#39;v&#39;, 0 ); // file comment length 
$cdrec .= pack(&#39;v&#39;, 0 ); // disk number start 
$cdrec .= pack(&#39;v&#39;, 0 ); // internal file attributes 
$cdrec .= pack(&#39;V&#39;, 32 ); // external file attributes - &#39;archive&#39; bit set 
$cdrec .= pack(&#39;V&#39;, $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; 
} 
function filezip(){ 
$data = implode(&#39;&#39;, $this -> datasec); 
$ctrldir = implode(&#39;&#39;, $this -> ctrl_dir); 
return 
$data . 
$ctrldir . 
$this -> eof_ctrl_dir . 
pack(&#39;v&#39;, sizeof($this -> ctrl_dir)) . // total # of entries "on this disk" 
pack(&#39;v&#39;, sizeof($this -> ctrl_dir)) . // total # of entries overall 
pack(&#39;V&#39;, strlen($ctrldir)) . // size of central dir 
pack(&#39;V&#39;, strlen($data)) . // offset to start of central dir 
"/x00/x00"; // .zip file comment length 
} 
} 
?>