Unzip WordPress (when using FTP)

unzipfile.php

<?php 

$file = 'wordpress-4.2.5.zip';
$path = pathinfo(realpath($file), PATHINFO_DIRNAME);
$zip  = new ZipArchive;
$res  = $zip->open($file);

if ($res === TRUE) {
  $zip->extractTo($path);
  $zip->close();
  echo "$file extracted to $path";
} 
else {
  echo "Cannot open $file";
}