api-client-php/doc/usage/examples/fetch_orders.md

That's how you can fetch the orders list:

<?php

use RetailCrm\Api\Interfaces\ClientExceptionInterface;
use RetailCrm\Api\Factory\SimpleClientFactory;
use RetailCrm\Api\Interfaces\ApiExceptionInterface;
use RetailCrm\Api\Model\Entity\CustomersCorporate\CustomerCorporate;

$client = SimpleClientFactory::createClient('https://test.retailcrm.pro', 'apiKey');

try {
    $response = $client->orders->list();
} catch (ApiExceptionInterface | ClientExceptionInterface $exception) {
    echo $exception; // Every ApiExceptionInterface instance should implement __toString() method.
    exit(-1);
}

foreach ($response->orders as $order) {
    printf("Order ID: %d\n", $order->id);
    printf("First name: %s\n", $order->firstName);
    printf("Last name: %s\n", $order->lastName);
    printf("Patronymic: %s\n", $order->patronymic);
    printf("Phone #1: %s\n", $order->phone);
    printf("Phone #2: %s\n", $order->additionalPhone);
    printf("E-Mail: %s\n", $order->email);

    if ($order->customer instanceof CustomerCorporate) {
        echo "Customer type: corporate\n";
    } else {
        echo "Customer type: individual\n";
    }

    foreach ($order->items as $item) {
        echo PHP_EOL;

        printf("Product name: %s\n", $item->productName);
        printf("Quantity: %d\n", $item->quantity);
        printf("Initial price: %f\n", $item->initialPrice);
    }

    echo PHP_EOL;

    printf("Discount: %f\n", $order->discountManualAmount);
    printf("Total: %f\n", $order->totalSumm);

    echo PHP_EOL;
}