How to unzip a zip file in the server.

<?php

$scriptfullpath=(empty($_SERVER["HTTPS"]) ? "http://" : "https://").$_SERVER["HTTP_HOST"].$_SERVER['PHP_SELF'];

$filename="";
$filename= $_POST["filename"];

echo <<< EOM
<form method="post" action="$scriptfullpath">
<input type="hidden" name="mode" value="unzip">
-----Un Zip program-----<BR>
Input zip filename:<input type="text" name="filename" value="$filename">
<input type="submit" value="UNZIP">
</form>
EOM;

if(strpos($filename,'.zip') !== false){

$zip = new ZipArchive;
$res = $zip->open($filename);
if ($res === TRUE) {
$zip->extractTo('./');
$zip->close();
echo 'OK--unzip success';
} else {
echo 'error--unzip failed';
}
}else{

if($_POST["mode"] == "unzip"){echo 'error--this file is not zip file';}
}

?>