<?php
define ("FILES_TO_KEEP", 5);
define ("BACKUP_PERIOD", 86400); // сутки
define ("DATABASE_CONF", 'mysql://mysql_login:mysql_password@mysql_server/database_name');
define ("BACKUP_FOLDER", './backup' );

error_reporting(0);

function cmp_file_times($t1, $t2) {
  if ($t1['t'] == $t2['t']) return 0;
  return ($t1['t'] > $t2['t']) ? 1 : -1;
}
function backup() {
  global $now;
  $file = BACKUP_FOLDER."/backup-".date("d-m-Y_H-i-s", $now).".sql";
  $db = parse_url(DATABASE_CONF);
  $db['path'] = substr($db['path'], 1);
  $q = "mysqldump -u".$db['user']." -p".$db['pass']." -h".$db['host']." ".$db['path']." > ";
  exec($q.$file."; gzip -f ".$file); // убедитесь что функции "mysqldump" и "gzip" доступны в консоли.
}
$now = time();
clearstatcache();
$b_dir = dir(BACKUP_FOLDER);
$b_files = array();
while($file = $b_dir->read()) {
  if (preg_match("/^backup-(\d+)-(\d+)-(\d+)_(\d+)-(\d+)-(\d+)/i", $file, $a)) {
    array_push($b_files, array('n' => $file, 't' => mktime($a[4], $a[5], $a[6], $a[2], $a[1], $a[3])));
  }
}
$b_dir->close();
$b_count_files = count($b_files);
if ($b_count_files) {
  usort($b_files, "cmp_file_times");
  if ($b_files[$b_count_files - 1]['t'] <= $now - BACKUP_PERIOD) {
    if ($b_count_files >= FILES_TO_KEEP) {
      for ($i = 0; $i < $b_count_files - FILES_TO_KEEP + 1; $i ++) {
		unlink(BACKUP_FOLDER."/".$b_files[$i]['n']);
      }
    }
    backup();
  }
}else {
  backup();
}
?>