mi risulta che onContextMenu funziona solo con Explorer, quindi con gli altri browser (Firefox-Chrome-safari-Opera) non funziona..occorre quindi ancora meglio un apposito script javascript che individua cosa fare per ogni browser..io di solito uso il seguente esempio
	Codice PHP:
	
<?php
  $button = $_REQUEST['button'];
  if ($button == 2) {
    $conn_id = ftp_connect($ftp_server);
    $login_result = ftp_login($conn_id, $ftp_user_name, $ftp_user_pass);
    if (ftp_delete($conn_id, $file)) {
      echo "$file deleted successful\n";
    } else {
      echo "could not delete $file\n";
    }
    ftp_close($conn_id);
  } 
?>
<html>
<head>
<title></title>
<script type="text/javascript">
        function WhichButton (event) {
            if (event.which === undefined) {    // Internet Explorer
                //left button pressed
                if (event.button & 1) {
                    location.href='stessa_pagina.php?button=1';
                }
               // right button pressed
                if (event.button & 2) {
                    location.href='stessa_pagina.php?button=3';
                    }
                }
                // middle button pressed
                if (event.button & 4) {
                    location.href='stessa_pagina.php?button=3';
                    }
                }
                alert ("The following buttons are pressed: " + buttons);
            }
            else {  // Firefox, Opera, Google Chrome and Safari
                switch (event.which) {
                case 1:
                    location.href='stessa_pagina.php?button=1';
                    break;
                case 2:
                    location.href='stessa_pagina.php?button=2';
                    break;
                case 3:
                    location.href='stessa_pagina.php?button=3';
                    break;
                }
            }
        }
    </script>
</script>
</head>
    <body>
      <table>
        <tr><td onmousedown="WhichButton (event);">file_1</td></tr>
        <tr><td onmousedown="WhichButton (event);">file_2</td></tr>
        <tr><td onmousedown="WhichButton (event);">file_3</td></tr>
      </table>
    </body>
</html>