PHP send slack messages with attachments and variable values

Question

Trying to send messages to slackchannels with incoming webhooks installed on them. Attachments needs to be sent along with the message and PHP variables holds these URLs. Similary, I want to send some ID's which are again hold in some PHP variables. Here is my server side PHP code:

<?php

$testplan_name = $_POST[plan]; //test plan name coming from the client
$url1 = $_POST[run_url]; //run url coming from the client
$url2 = $_POST[plan_url]; //plan url coming from the client
$room = "random"; 
$icon_url = ":ghost:";
$username = "Test";
$attachments = array([
            'fallback' => 'Hey! See this message',
            'pretext'  => 'Here is the plan name ${testplan_name}',
            'color'    => '#ff6600',
            'fields'   => array(
                [
                    'title' => 'Run URL',
                    'value' => 'url1',
                    'short' => true
                ],
                [
                    'title' => 'Build URL',
                    'value' => 'url2',
                    'short' => true
                ]
            )
        ]);

$data = "payload=" . json_encode(array(         
        "channel"       =>  "#{$room}",
        "icon_emoji"    =>  $icon_url,
        "username"      =>  $username,
        "attachments"   =>  $attachments

    ));

$url = "https://hooks.slack.com/services/XXXX/XXX/XXXXXXXXXXXXX"; //got from slack as a webhook URL

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
$result = curl_exec($ch);
echo var_dump($result);
if($result === false)
{
    echo 'Curl error: ' . curl_error($ch);
}

curl_close($ch);

If you see in the attachments variable above, there is variable inside of pretext which tries to print the value of ${testplan_name} declared at the top. However, it does not seem to work and the program is failed to post messages to slack channels. Similarly, I want to print values of url1 and url2 in the attachments -> fields values as can be seen above(the way I am trying to print). The program just works fine if I do not try to use any variables and get their values while posting messages. How do I print the values of these variables in messages?

(slack is a messaging platform for teams, if you don't know)

Answer 1

Try this instead>

    $attachments = array([
        'fallback' => 'Hey! See this message',
        'pretext'  => 'Here is the plan name '.$testplan_name,
        'color'    => '#ff6600',
        'fields'   => array(
            [
                'title' => 'Run URL',
                'value' => $url1,
                'short' => true
            ],
            [
                'title' => 'Build URL',
                'value' => $url2,
                'short' => true
            ]
        )
    ]);