PHP RESTful服务; 带有用户名/密码凭据的AJAX和DELETE方法

I asked another question related to RESTful services here, and have another question involving DELETE (PUT):
Same kind of situation where I want to send along user credentials (username/password) with my PUT. This is my DELETE service so far:

$http_req   = $_SERVER["REQUEST_METHOD"];
switch ($http_req) {
    case DELETE:
        $user = $acct->read($_REQUEST["usernameDel"], $_REQUEST["passwordDel"]);  // this method used to read db table with 1 record
        if (!empty($_REQUEST["delTaskId"]) && isset($_REQUEST["usernameDel"]) && isset($_REQUEST["passwordDel"])) {
            if ($user == true) {
                $delete     = fopen("php://input", "r");
                $data       = stream_get_contents($deleted);
                $params;
                parse_str($data, $params);
                $dropped = $mgr->delete($params["id"])  // calls the method that deletes a particular row based on its id
                echo $dropped;
            }
        }                
}

This is the html page I am working with. I updated it to be in a :

<form action="TaskService.php" method="POST">
<label for="usernameDel">Username</label>
    <input type="text" name="usernameDel" id="usernameDel" required/><br />
<label for="passwordDel">Password</label>
    <input type="password" name="passwordDel" id="passwordDel" required/><br />
<label for="delTaskId">Task ID</label>
    <input type="text" name="delTaskId" id="delTaskId" required/><br /><br />
<button type="button" id="btnDelete">Delete Task</button><br /><br />
</form>

This is my ajax code (edit-now using @Devs modifications):

$("#btnDelete").click(function() {

    $.ajax({
            method: "DELETE",  
            url: "TaskService.php",  
            data: { 'username':$("#usernameDel").val(), 'password': $("#passwordDel").val(), 'id': $("#delTaskId").val()},
            success: function(theResponse) {
                alert(theResponse);
            }
        });
});

Currently it returns a 200 response, but gives me the error messages I had put in for my Account class (comes back with "Could not find account".

My gut is telling me it has something to do with my $_REQUEST[] superglobals since it's not doing anything with a form action, but I am not all too familiar with passing information via ajax
Thoughts?

Just arranged the ajax format, also some syntax error in the php code.

Note: never tested

Ajax

$(document).ready(function(){ 

   $("#btnDelete").click(function() {

        $.ajax({
                method: "DELETE",  
                url: "TaskService.php",  
                data: { 'username':$("#usernameDel").val(), 'password': $("#passwordDel").val(), 'id': $("#delTaskId").val()},
                success: function(theResponse) {

                    // Output 
                    alert(theResponse); // comment this

                    }  
            });
    });
});                 

TaskService.php

<?php
$http_req   = $_SERVER["REQUEST_METHOD"];

switch ($http_req) {
    case DELETE:
        $user = $acct->read($_REQUEST["username"], $_REQUEST["password"]);  // this method used to read db table with 1 record
        if ($user == true) {
            $delete     = fopen("php://input", "r");
            $data       = stream_get_contents($deleted);
            $params;
            parse_str($data, $params);
            $dropped = $mgr->delete($params["id"]);  // calls the method that deletes a particular row based on its id
            echo $dropped;
        }
    break;
}
?>

Found out why my validation wasn't working! I feel so blind!
I was ignoring the fact that the delete action was taking username, password, and id as parameters....as such, validation wasn't going to work because the "php://input" file hadn't been opened to parse through all 3 parameters.
Here's my updated PHP that works:

// I needed to access the file FIRST before doing anything with the parameters passed from AJAX
$deleted    = fopen("php://input", "r");
$data       = stream_get_contents($deleted);
$params;
parse_str($data, $params);

$user_auth  = $acctMgr->readAcct($params["username"], $params["password"]);
        if ($user_auth == true) {
            $rows   = $mgr->delete($params["id"]);

            echo $rows;
        } else {
            echo "User not authenticated";
        }