Check request and finalize response

check-request.php

<?php

function err($err)
{
    $res['state'] = false;
    $res['err'] = $err;
    echo json_encode($res);
    die();
}

function check($query, $err)
{
    if (!isset($_REQUEST[$query])) {
        err($err);
    }
}

function complete($data)
{
    $res['state'] = true;
    $res['data'] = $data;
    echo json_encode($res);
    die();
}

$data = array();

extract($_REQUEST);

?>