if(isset($_POST['login'], $_POST['pass'])){
if(preg_match('|^[a-zа-яА-Я\d\.\-]{5, 12}$|iu', $_POST['login'])){
if(strlen(trim($_POST['pass'])) > 5 AND strlen(trim($_POST['pass'])) < 25 ){
$prov = mysql_fetch_assoc(mysql_query("SELECT id FROM `users` WHERE `login`='".$login."';"));
if($prov['id']==''){
mysql_query("INSERT INTO `users`
(`login`, `password`, `pass_nomd5`, `date_reg`, `real_date`, `sex`, `about`)
VALUES
('".$login."', '".md5(trim($_POST['pass']))."', '".htmlspecialchars(trim($_POST['pass']), ENT_QUOTES)."', '". date("d.m.Y в H:i") ."', '". date("d.m.Y в H:i") ."', '".htmlspecialchars(trim($_POST['sex'], ENT_QUOTES))."', 'Не заполнено');
");
/* executed */
}else{
/* login is already occupied */
}
}else{
/* bad password */
}
}else{
/* bad login */
}
}else{
/* this form */
}