How to force download a .rtf file in PHP? -

so code have used button download wordpad .rtf file following:

my php script:

 <?php       if(isset($_post['file_name'])){     $file = $_post['file_name'];     header('content-type: application/rtf');     header('content-disposition: attachment; filename="'.$file.'"');     readfile('uploads/'.$file);     exit();     } 

and div associated:

<div class ="buttonhol">     <h2> <center> holiday request form </center> </h2>     <form action="rota.php" method="post" name="downloadform">   <input name="file_name" value="holidayrequestform.rtf" type="hidden">   <input type="submit" value="download holiday request form">     </div> 

-- have used exact same code excel file in same folder 'uploads' content-type matches appropriate. when click 'download holiday request form' button.. document gets downloaded titled correctly file contains code written in particular php class.

what doing wrong?

many in advance.