Passing Multiple variables into JSON using ajax and data- off link

Question

Background

I have a web application which uses a link and a jQuery handler to submit information through ajax to perform a function in an outside PHP file....
I am receiving this error on passing the variables

PHP Fatal error: Function name must be a string in..... on line 7 (check comment of php)

What exactly am I doing wrong?

Link Which is Passing information

<a href="#" id="tester" data-letterid="13" data-type="failValidate">This Link Fails</a>

jQuery

$('#tester').on("click",function(){ 
    var dataObj = {}
    dataObj['letterid']=$('#tester').attr("data-letterid");
    dataObj['letterid']=JSON.stringify(dataObj['letterid']);
    dataObj['type']=$('#tester').attr("data-type");
    dataObj['type']=JSON.stringify(dataObj['type']);
    $.ajax({
        url: 'super_testy.php',
        type: 'POST',
        data: dataObj,
        dataType: 'json',
        success: function(data){
            alert("success!!");

            return false;
        },
        error: function(jqXHR, textStatus, errorThrown){
            alert(textStatus);}
        });});

PHP File Abstract

//It Fails Right Here, and says that Fatal Error, shown above
$id=$_POST('letterid');
$type=$_POST('type');
if ($type == "failValidate") { //do something, etc....}

Even after testing and adding JSON.stringify(xyz) to the variables doesn't seem to help

Answer 1

The $_POST, $_GET, $_REQUEST superglobals are arrays, so you need to access them with bracket notation, not like a function:

$id = $_POST['letterid'];
$type = $_POST['type'];