Compress files into a single zip file

createZip.php

<?php

/**
 * @file
 * Creates a compressed zip file.
 *
 * @author Original Author: David Walsh
 * @author Modified by: Nick Mathew
 * @link https://davidwalsh.name/create-zip-php
 */

/**
 * Compress files into a single zip file.
 *
 * @param string $files
 *   Array of location of files that need to be zipped.
 * @param string $destination
 *   (Optional) Destination path to save the zip file.
 * @param int $overwrite
 *   (Optional) Overwrite the file if it already exists. Defaults to false.
 *
 * @return bool
 *   Returns true if successful.
 */
function createZip($files = array(), $destination = '', $overwrite = FALSE) {

  // If the zip file already exists and overwrite is false, return false.
  if (file_exists($destination) && !$overwrite) {
    return FALSE;
  }

  $valid_files = array();

  if (is_array($files)) {
    // Cycle through each file and make sure that each file exists.
    foreach ($files as $file) {
      if (file_exists($file)) {
        $valid_files[] = $file;
      }
    }
  }
  if (count($valid_files)) {
    $zip = new ZipArchive();
    if ($zip->open($destination, $overwrite ? ZIPARCHIVE::OVERWRITE : ZIPARCHIVE::CREATE) !== TRUE) {
      return FALSE;
    }

    foreach ($valid_files as $file) {
      // Remove directory structure.
      $new_filename = substr($file, strrpos($file, '/') + 1);
      $zip->addFile($file, $new_filename);
    }

    $zip->close();

    // Check to make sure the file exists.
    return file_exists($destination);
  }
  else {
    return FALSE;
  }
}