test.html
<!DOCTYPE html>
<html>
<title>LicAPI - Submit a license</title>
<body>
<form action="api.php" method="post">
License:<br>
<input type="text" name="license" value="Test">
<br><br>
<input type="submit" value="Submit">
</form>
<p>Click the submit button to check your license.</p>
</body>
</html>