Форма
if (isset($_POST['submit'])) {
file_put_contents('./baner.txt', $_POST['baner']);
} else {
echo '<form action="" method="post"><input type="text" name="baner" /><br/><input type="submit" name="submit" value="ok" /></form>';
} Форма
if (isset($_POST['submit'])) {
file_put_contents('./baner.txt', $_POST['baner']);
} else {
echo '<form action="" method="post"><input type="text" name="baner" /><br/><input type="submit" name="submit" value="ok" /></form>';
}