Detect when browser receives file download From:http://stackoverflow.com/questions/1106377/detect-when-browser-receives-file-download

Client.js

function getCookie( name ) {
    var parts = document.cookie.split(name + "=");
    if (parts.length == 2) return parts.pop().split(";").shift();
  }

  function expireCookie( cName ) {
    document.cookie = 
      encodeURIComponent( cName ) +
      "=deleted; expires=" +
      new Date( 0 ).toUTCString();
  }

  function setCursor( docStyle, buttonStyle ) {
    document.getElementById( "doc" ).style.cursor = docStyle;
    document.getElementById( "button-id" ).style.cursor = buttonStyle;
  }

  function setFormToken() {
    var downloadToken = new Date().getTime();
    document.getElementById( "downloadToken" ).value = downloadToken;
    return downloadToken;
  }

  var downloadTimer;
  var attempts = 30;

  // Prevents double-submits by waiting for a cookie from the server.
  function blockResubmit() {
    var downloadToken = setFormToken();
    setCursor( "wait", "wait" );

    downloadTimer = window.setInterval( function() {
      var token = getCookie( "downloadToken" );

      if( (token == downloadToken) || (attempts == 0) ) {
        unblockSubmit();
      }

      attempts--;
    }, 1000 );
  }

  function unblockSubmit() {
    setCursor( "auto", "pointer" );
    window.clearInterval( downloadTimer );
    expireCookie( "downloadToken" );
  }

serve.php

 $TOKEN = "downloadToken";

    // Sets a cookie so that when the download begins the browser can
    // unblock the submit button (thus helping to prevent multiple clicks).
    // The false parameter allows the cookie to be exposed to JavaScript.
    $this->setCookieToken( $TOKEN, $_GET[ $TOKEN ], false );

    $result = $this->sendFile();

where.php

public function setCookieToken(
    $cookieName, $cookieValue, $httpOnly = true, $secure = false ) {

    // See: http://stackoverflow.com/a/1459794/59087
    // See: http://shiflett.org/blog/2006/mar/server-name-versus-http-host
    // See: http://stackoverflow.com/a/3290474/59087
    setcookie(
      $cookieName,
      $cookieValue,
      2147483647,            // expires January 1, 2038
      "/",                   // your path
      $_SERVER["HTTP_HOST"], // your domain
      $secure,               // Use true over HTTPS
      $httpOnly              // Set true for $AUTH_COOKIE_NAME
    );
  }