Game-Jaming/Backend/Controllers/Group/GetGroup.php

<?php
require_once "../../../bootstrap.php";
use Backend\Models\Group;

if (isset($_POST["groupId"])){
$groups = Group::find($_POST["groupId"]);
}
elseif(isset($_POST["gameJameId"])){
    $groups = Group::where("game_jam_id",$_POST["gameJameId"]);
}
else{
    $groups = Group::all();
}

header('Content-Type: application/json;charset=UTF-8');
echo $groups->toJson(JSON_PRETTY_PRINT);