<?php
$brand = json_decode(file_get_contents('marka_json_url'));

foreach ($brand->markalist as $item) {
    $data = json_decode(file_get_contents('https://xxx.com/xxxx?marka=' . $item->marka, false, stream_context_create($arrContextOptions)));

    if (count($data->urunkList)) {
        foreach ($data->urunkList as $idx => $urunkList) { 
            // bla bla
        }
    } 
}