<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>test page</title>
</head>
<body>
<p>
<?php
echo "value of the post:" . htmlspecialchars($_POST['example']);
?>
</p>
<form method="post" action="<?=htmlspecialchars($_SERVER['SCRIPT_NAME']);?>">
<input type="text" name="example" />
<input type="submit" />
</form>
</body>
</html>