Simple PHP editor of text files

To read the file:

<?php
    $file = "pages/file.txt";
    if(isset($_POST))
    {
        $postedHTML = $_POST['html']; // You want to make this more secure!
        file_put_contents($file, $postedHTML);
    }
?>
<form action="" method="post">
    <?php
    $content = file_get_contents($file);
    echo "<textarea name='html'>" . htmlspecialchars($content) . "</textarea>";
    ?>
    <input type="submit" value="Edit page" />
</form>

You create a HTML form to edit the text-file's content. In case it get's submitted, you update the text-file (and redirect to the form again to prevent F5/Refresh warnings):

<?php

// configuration
$url = 'http://example.com/backend/editor.php';
$file = '/path/to/txt/file';

// check if form has been submitted
if (isset($_POST['text']))
{
    // save the text contents
    file_put_contents($file, $_POST['text']);

    // redirect to form again
    header(sprintf('Location: %s', $url));
    printf('<a href="%s">Moved</a>.', htmlspecialchars($url));
    exit();
}

// read the textfile
$text = file_get_contents($file);

?>
<!-- HTML form -->
<form action="" method="post">
<textarea name="text"><?php echo htmlspecialchars($text); ?></textarea>
<input type="submit" />
<input type="reset" />
</form>