<!DOCTYPE html>
<html>
<body>
<form method="get" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
E-mail: <input type="text" name="email">
<input type="submit" name="submit" value="Submit">
</form>
<?php
if (isset($_GET["email"])) {
if (!filter_input(INPUT_GET, "email", FILTER_VALIDATE_EMAIL) === false) {
echo("Email is valid");
} else {
echo("Email is not valid");
}
}
?>
</body>
</html>