How to create a zip file in php?

 $zip = new ZipArchive();  
 $file_name = "./myzip.zip";  
 if ($zip->open($file_name, ZIPARCHIVE::CREATE) !== TRUE) {  
   exit("cannot open <$file_name>\n");  
 }  
 try {  
   //it will create new file add content   
   $zip->addFromString("test_my_file.txt" . time(), "#1 String for testingsave as test_my_file.txt.\n");
   //first part of original file and second part you wnat give name of file in zip  
   $zip->addFile("test1.php", "test1.php") or die ("ERROR: Could not add file:");  
   $zip->addFile("test2.php", "test2.php") or die("ERROR: Could not add file:");  
   //test1.php and test2.php files must be exist  
 } catch (Exception $e) {  
   echo $e->getMessage();  
   exit;  
 }  
 echo "Zipped Files : " . $zip->numFiles . "\n";  
 echo "Status of Zip :" . $zip->status . "\n";  
 $zip->close();