LiqPay does not have API for checkout page URL creator (online payment page). It is possible to retrieve this URL from the LiqPay API response headers. This class solves this task.
More information about parameters you can find at LiqPay documentation.
$apiParams = [
'public_key' => 'some_public_key',
'private_key' => 'some_private_key'
];
$paymentParams = [
'action' => 'pay',
'amount' => '1',
'currency' => 'USD',
'description' => 'description text',
'order_id' => 'order_id_1',
'version' => '3'
];
$url = LiqPayCheckoutUrlCreator::create(
$apiParams,
$paymentParams
);