Edit.php

<?php

// Get the file name
$file_name = $_GET['name'];

// Read file
$file_read = fopen($file_name,"r");

// Get the contents
$contents = fread($file_read, filesize($file_name));

fclose($file_read);

?>
<html>

<form action="edit_file.php" method="POST">

        <textarea name="edit" cols="100" rows="20"><?php echo $contents;  ?></textarea><p>
        <input type="hidden" name="file_name" value="<?php echo $file_name; ?>">
        <input type="submit" value="Save ME!">
    </form>
   <head>
<style>
  body {background-color:lightgrey}
</style>
</head>
</html>