Pass javascript variable to .php file [duplicate]

Question

I have two file one charts.js and the other getdata.php. The charts.js file has a variable campaignId (this is an number) which I need to pass to my getdata.php file where I want to put campaignId in a MySQL query. The issue is that the value is not getting passed to the php file. how do I resolve this issue. Thanks

I am running all my code locally. Using MAMP. All my code files are in one folder and the path is given to MAMP.

In the charts.js file this is what I am writing.

function  category(camp_id){   
        camp = camp_id;   
        $.ajax({   
        type: "POST",   
        url: "http://localhost:8888/getdata8.php",   
        data: camp,   
        error:function() {   
                alert("sorry")   
        },   
       success: function(result) {   
           alert(result);   
       }   
    });   
}  

In my PhP I am doing:

$id= $_POST['camp'];

Answer 1

Pass an object to data:

data: {
    camp: camp_id
}

Answer 2

You may not be declaring/setting camp correctly, it should be something like the below:

var camp = "camp=" + camp_id;