How to set up twilio taskrouter outbound call?

Question

I am trying to set up outgoing calls through Twilio task router. I am creating tasks through PHP with the all the necessary attributes (instruction, to , from, post_work_activity_sid ) but the created task doesn't set up a call between the twilio client and the external phone number. I was hoping that tasks created by the program would create a conference call between worker(browser) and external client. I keep getting an error that is shown below. I have a assignment php on my application server which de-queues calls to my workers (Browser clients). Currently, incoming calls from external number to browser clients through task router is working as expected. However, outbound calls generates a task and a reservation is assigned but Twilio is not able to dequeue the call to a worker. Is there a way to create a task for voice call such that the task is created using Twiml Enqueue verb? Or is there a better way of handling outbound calls using the Twilio taskrouter so that calls are assigned successfully to the workers using Browser client ?

As per this thread: Can outbound calls be made through Twilio TaskRouter , I tried using instruction call.I have also gone through the documentation and another stack overflow post about assignment callback URL but it's not clear and am not sure what I could be potentially doing wrong.

Error message: The dequeue instruction can only be issued on a task that was created using the TwiML verb

<?php
require_once('TwilioVendor/autoload.php'); // Loads the library
use Twilio\Rest\Client;
$sid    = "ACxxxxxxxxxxxxxxxxxxxxxxx";
$token  = "xxxxxxxxxxxxxxxxxxxxxxxxxxx";
try{
$twilio = new Client($sid, $token);
$task = $twilio->taskrouter->v1- 
>workspaces("WSxxxxxxxxxxxxxxxxxxxxxxxxxxxx")->tasks- 
>create(array("attributes" => json_encode(array(
//"instruction"=>"accept",
//"instruction"=>"conference",
"instruction"=>"call",
"to"=> "client:Bob",
"from"=> "+61123456789",
"post_work_activity_sid"=> "WAxxxxxxxxxxxxxxxxxxxx"
)),
"workflowSid" => "WWxxxxxxxxxxxxxxxxxx"
)
);
}catch(Exception $e)
{
echo 'Caught exception: ',  $e->getMessage(), "\n";
}
print($task->sid);

**Assignment Callback code**   

<?php
$assignment_instruction = [
'instruction' => 'call','to'=> 'client:Bob',
'from' => '+61xxxxx','url'=>'CRM REST END POINT'
];

header('Content-Type: application/json');
echo json_encode($assignment_instruction);

**CRM REST END POINT TWIML**
<?php
require __DIR__ . '/vendor/autoload.php';
require_once 'TwilioVendor/autoload.php'; 
use Twilio\Twiml;
$reservationSid= $_REQUEST['rsid']
header('Content-Type: text/xml');
?>
<?xml version="1.0" encoding="UTF-8"?>

<Response>
<Say voice="woman">You will now be connected to the customer</Say>
<Dial>
<Queue reservationSid="<?$reservationSid?>"/>
</Dial>
</Response> 

Answer 1

Twilio developer evangelist here.

TaskRouter will only generate calls to your workers when a task is created by the <Enqueue> TwiML verb. Creating a task with the REST API, even if you add call attributes, will not generate a call when you use the dequeue or call instruction.

Instead, you will need to manage the task and call yourself. When your worker is sent the reservation and accepts it, you should use the REST API to create the call , connect it to your browser client and then dial out to the end user.