form.php

<?php
if (isset($_POST['Submit'])) {
    $file = fopen('Data.lua','a+');
    $code = $_POST['code'];
    fwrite($file,$code);
    fclose($file);
}

if (isset($_POST['Clear'])) {
    $file = fopen('Data.lua', 'w');
    fclose($file);
}

?>
<form action='form.php' method='post'>
    <legend>Execute:</legend>
    Code (lua) :
    <input type='text' name='code' size= '30'/>
    <input type='submit' name='Submit' value='Submit'/>
    <input type='submit' name='Clear' value='Clear' />
</form>