<?php
$webhooksbase = 'https://api.atlassian.com/ex/jira/'.$site_id.'/rest/api/3/webhook';
$data = <<<REQUESTBODY
    {
      "url": "https://webhook.site/839d3c82-5da3-454f-9b70-52f33dc4c6ed",
      "webhooks": [
        {
          "events": [
            "jira:issue_updated"
          ],
          "fieldIdsFilter": [
            "summary"
          ],
          "jqlFilter": "project = TESTRAIL"
        }
      ]
    }
REQUESTBODY;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $webhooksbase);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Accept: application/json',
    'Content-Type: application/json',
    'Authorization: Bearer ' . $result_decode['access_token']
]);
$result_issue = curl_exec($ch);
$httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

if (curl_errno($ch)) {
    echo 'Error:' . curl_error($ch);
}
curl_close($ch);
echo 'code:'. $httpcode.'<hr />Response: <br>';

?>