在php中使用javascript数据错误

Using this ajax code i am passing data speedMbps from my javascript to php. however when i tried to use the speedMbps in php i am getting a Undefined index: speedMbps. what should i do so i can use speedMbps in php?

Edited: video_id is send using html form post.

$.ajax({
          method: "POST",
          url: "viewvideo.php",
          data: {speedMbps: speedMbps },
          cache: false
        }).done(function( html ) {
            $( "#speed" ).val( html );
    });

php file

if(isset($_POST['video_id']) && ( $_POST['speedMbps'] )){
$speed = $_POST['speedMbps'];
if ($speed < 100) {

                }

Try something like this :

$.ajax({
          method: "POST",
          url: "viewvideo.php",
          data: {"speedMbps" : speedMbps,"video_id":video_id },
          cache: false
        }).done(function( html ) {
            $( "#speed" ).val( html );
    });

try this:

$.ajax({
      method: "POST",
      url: "viewvideo.php",
      data: {speedMbps: "speedMbps" },
      cache: false
    }).done(function( html ) {
        $( "#speed" ).val( html );
});

here you checking two varibales with AND condition but passing only one variable. so you can change AND condition to OR and try it.

if(isset($_POST['video_id']) || isset( $_POST['speedMbps'] )){  //missing isset function here. also change AND to OR  

Or you have to pass video_id also in ajax function like this:

 data: {speedMbps: speedMbps, video_id:video_id },

you need to put speedMbps in single quotes.

data: {'speedMbps': speedMbps },

You either need to send video_id with AJAX request or you can remove the condition in php and check since in php you are checking if video_id is set or not, if(isset($_POST['video_id']) && ( $_POST['speedMbps'] )){

$.ajax({
          method: "POST",
          url: "viewvideo.php",
          data: {
            speedMbps: speedMbps,
            video_id:  VIDEO_ID_PUT_HERE //`video_id: $('[name="video_id"').val()`
          },
          cache: false
        }).done(function( html ) {
            $( "#speed" ).val( html );
    });

in your php:

if(isset($_POST['video_id']) && isset($_POST['speedMbps'] )){
  $speed = $_POST['speedMbps'];
   if ($speed < 100) {
   //do your stuff
   }
}

var speedMbps ='' //here is Your value for speedMbps
var videoid = //here  is Your value for video id    
$.ajax({
          method: "POST",
          url: "viewvideo.php",
          data: {speedMbps: speedMbps ,videoid:videoid},
          cache: false,
       success:(function( html ) {
            $( "#speed" ).val( html );
    });