How to set up a PHP Curl POST request which can trigger via a JavaScript onclick event?

I want to track the button click event which is Submit button in javascript to curl PHP side and the url in php file will send the event that I trigger and stored into the database.

Below are 2 files that I make, the 1st part is ajax, and then 2nd part is PHP.

May anyone help me please? Thank you.

(function($){
$("_form_44__submit").on('click', function () {
    // fire the AJAX request on button click
    $.ajax({
       type: "POST",
       url: 'curl.php',
       dataType: 'json',
       headers: {"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",},
       data: {actid: "actid",
    key: "key",
    event: "Click_Submit_Button_Event",
    visit: ["email"]
 },
    })
    .done(function (response) {
        console.log(response);
       // if you want to do something on success
    })
    .fail(function (xhr, status, error) {
        console.log('error');
       // if you want to do something on error
    });
  });
})

<?php


$actid = $_POST['actid'];
$key =  $_POST['key'];
$event =  $_POST['event'];
$visit =  $_POST['visit'];

$url = "https://trackcmp.net/event";

    $curl = curl_init(); //open connection /
    // changes the cURL session behavior with options POST
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    //curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($curl, CURLOPT_POSTFIELDS, array(
        'actid' => $actid,
        'key' => $key,
        'event' => $event,
        'visit' => $visit,
));
    //execute
    $result = curl_exec($curl); //handle $curl_init
    if ($result !== false) {
        $result = json_decode($result);
        if ($result->success) {
            echo 'Success! ';
        } else {
            echo 'Error! ';
        }

        echo $result->message;
    } else {
        echo 'cURL failed to run: ', curl_error($curl);
    }


?>