Unzip Zip File

<?php
/**********************
*@file - path to zip file
*@destination - destination directory for unzipped files
*/
function unzip_file($file, $destination){
  // create object
	$zip = new ZipArchive() ;
	// open archive
	if ($zip->open($file) !== TRUE) {
		die ("Could not open archive");
	}
	// extract contents to destination directory
	$zip->extractTo($destination);
	// close archive
	$zip->close();
	echo 'Archive extracted to directory';
}

Zip Files on the Fly

<?php
/* creates a compressed zip file */
function create_zip($files = array(),$destination = '',$overwrite = false) {
  //if the zip file already exists and overwrite is false, return false
	if(file_exists($destination) && !$overwrite) { return false; }
	//vars
	$valid_files = array();
	//if files were passed in...
	if(is_array($files)) {
		//cycle through each file
		foreach($files as $file) {
			//make sure the file exists
			if(file_exists($file)) {
				$valid_files[] = $file;
			}
		}
	}
	//if we have good files...
	if(count($valid_files)) {
		//create the archive
		$zip = new ZipArchive();
		if($zip->open($destination,$overwrite ? ZIPARCHIVE::OVERWRITE : ZIPARCHIVE::CREATE) !== true) {
			return false;
		}
		//add the files
		foreach($valid_files as $file) {
			$zip->addFile($file,$file);
		}
		//debug
		//echo 'The zip archive contains ',$zip->numFiles,' files with a status of ',$zip->status;
		
		//close the zip -- done!
		$zip->close();
		
		//check to make sure the file exists
		return file_exists($destination);
	}
	else
	{
		return false;
	}
}
/***** Example Usage ***/
$files=array('file1.jpg', 'file2.jpg', 'file3.gif');
create_zip($files, 'myzipfile.zip', true);