This PHP code is designed to handle zip file extraction - unzip based on a 'zip' parameter provided through a GET request.

unzipper.php

<?php
// Check if the 'zip' parameter is empty in the GET request.
if(empty($_GET['zip'])){
	// If 'zip' parameter is empty, terminate the script and display 'No zip!' message.
	die('No zip!');
}
// Create a new instance of the ZipArchive class.
$zip = new ZipArchive;

// Try to open the zip file specified in the 'zip' parameter.
$res = $zip->open($_GET['zip']);

// Check if the zip file was successfully opened.
if ($res === TRUE) {
	// If the zip file was opened successfully, extract its contents to the current directory.
	$zip->extractTo('./');
	
	// Close the zip file.
	$zip->close();
	
	// Display 'Ok' to indicate successful extraction.
	echo 'Ok';
} else {
	// If the zip file couldn't be opened, display 'Not ok' to indicate an error.
	echo 'Not ok';
}