<form action='add.php' method='POST'>
 <input type='text' name='file_name' size='78' value='имя фала'>
 <textarea name='file_text' rows='8' cols='70'>
 </textarea>
 <input class='button' type='submit'>
</form>

$file_name=htmlspecialchars(stripslashes($_POST['file_name']));
$file_text=htmlspecialchars(stripslashes($_POST['file_text']));

if (copy ($file, "file/$file_name"))
 {
  $TheFileadd = "file/$file_name";
  $Open = fopen ($TheFileadd, "a");
  if ($Open)
   {
     fwrite ($Open, "$file_text");
     fclose ($Open);
   }
 }