var u = "CENTRAL\myusername";
    var p = "myp@ssword";
    var payload = {
        username: u,
        password: p,
        client: 'referer',
        referer: 'https://mycompany.com/myapp',
        expiration: '60',
        format: 'json',
    };
    var tokenUrl = 'https://gis.mycompany.com/public/tokens/generateToken';
    $.ajax({
        url: tokenUrl,
        type: "POST",
        crossDomain: true,
        dataType: 'text',
        data: payload,
        success: function(data){
            token = data;
            console.log(token)
        }
    });

$GISuser = "CENTRAL\myusername";
    $GISpassword = "myp@ssword";
    $GISurl = "https://gis.mycompany.com/public/tokens/generateToken";
    $payload = array(
        "username" => $GISuser,
        "password" => $GISpassword,
        "client" => "referer",
        "referer" => 'https://mycompany.com/myapp',
        "expiration" => "60",
        "format" => "json"
    );

    $curl = curl_init();
    curl_setopt($curl, CURLOPT_POST, 1);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $payload);
    curl_setopt($curl, CURLOPT_URL, $GISurl);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);

    $result = curl_exec($curl);
    curl_close($curl);

    echo $result;