<html>
<head>
<title>titolo<title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>

<form name="miaform" method="POST" action="<?php echo $_SERVER['PHP_SELF']; ?> ">

user: <input type="text" name="text1">
password: <input type="text" name="text2">
<input type="button" name="submit" value="submit">

</form>

code:
<?php
if (isset($_POST['submit'])) {
echo "OK";
}
else {
echo "KO";
}
?>

</body>
</html>