my little handy backup from php

<?php
  if ($_POST){
  $nap=stripslashes($_POST['nap']);
  exec ("find /var/www/ize -not -name \"backup_*\" -a -not -name \"backup.php\" -a -not -name \"*.zip\" -a -not -name \"error.log\" -a -not -path \"*/zend*\" -a -not -path \"*tmp/*\" -a -not -path \"*images/*\" -a -not -path \"*fotok*\" -type f -mtime -$nap > lista");
$fajl = "backup_".`date +%F_%H%M`.".tar.gz";
$output = `tar -cvzf /var/www/ize/backup_\`date +%F_%H%M\`.tar.gz --files-from lista`;
                  echo "DONE!";
                  echo "<a href=\"$fajl\">backup</a>";
                  echo "<pre>$output</pre>";
  } else {
  ?>
  <form action="backup.php" method="post">
  file age limit to be backuped ?
  <input type="text" name="nap" id="nap" cols="2" rows="1">
  <button class="button" type="submit">GO</button>
  </form>
<?php }; ?>