Hacky workaround for apparent Guzzle issue when uploading JSON body > 1MB

uploadEticketsForAnOrder.php

function uploadEticketsForAnOrder(array $array = [], $token, $secret)
{
    $orderId = $array['order_id'];
    $url = 'https://api.ticketevolution.com/v9/orders/' . $orderId . '/deliver_etickets';

    $data_string = '{"etickets":' . json_encode($array['etickets']) . '}';

    $stringToSign = 'POST ' . preg_replace('/https:\/\/|\?.*/', '', $url) . '?' . $data_string;
    $signature = base64_encode(hash_hmac('sha256', $stringToSign, $secret, true));

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_VERBOSE, false);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json',
        'Content-Length: ' . strlen($data_string),
        'X-Token: ' . $token,
        'X-Signature: ' . $signature,
        'Expect:',
        'Accept: application/json',
    ]);

    $result = curl_exec($ch);

    curl_close($ch);

    return $result;
}

Example:

$item = new stdClass();
$item->item_id = $orderItem;
$item->eticket = base64_encode(file_get_contents('path-to-tickets.pdf'));

try {
    $result1 = uploadEticketsForAnOrder([
            'order_id' => $orderNumber,
            'etickets' => [$item]
        ],
        'TEVO_API_TOKEN',
        'TEVO_API_SECRET'
    );
    // var_dump($result1);
} catch (\Exception $e) {
    // Handle exception
}