question

We have experienced the same with our Payeezy integration. We partially migrated our code to Clover but that platform is having issues as well. The webhook does not work in the sandbox environment and neither the webhook or the redirect urls work in production.

You want to create an Ecommerce API token for Hosted Checkout.

Here is the snippet you asked for to retrieve a Clover hosted checkout URL, you will want to redirect the user to that URL to complete the payment.

$url = 'https://www.clover.com/invoicingcheckoutservice/v1/checkouts';
$data = [
    "customer" => [
        "email" => "jane@doe.com",
    ],
    "shoppingCart" => [
        "lineItems" => [
            [
                "name" => "ACME Widgets",
                "unitQty" => 1,
                // this is $10.00
                "price" => 1000
            ]
        ]
    ],
];
$headers = [
    'X-Clover-Merchant-Id: XXXXXXXXXXXXXXXXXXXXXX',
    'Authorization: Bearer XXXXXXXXXXXXXXXXXXXXXX',
    'Accept: application/json',
    'Content-Type: application/json',
];

$opts = [
    'http' => [
        'method' => 'POST',
        'header' => implode("\r\n", $headers),
        "ignore_errors" => true,
        'content' => json_encode($data),
    ]
];
$context = stream_context_create($opts);
$response = file_get_contents($url, false, $context);
echo json_decode($response);

You can also use curl as well if you prefer.

Good luck.