Gravity Forms and Easy Digital Downloads Licensing: Sample licensing class that you can use to set up licenses with a Gravity Forms add-on.

gf-edd-license-helper.php

<?php
// don't load directly.
if ( ! defined( 'ABSPATH' ) ) {
	die();
}

/**
 * Gravity Forms ClickUp Add-On.
 *
 * @since     1.0.0
 * @package   tazker-for-clickup
 * @author    Ronald Huereca
 * @copyright Copyright (c) 2022, MediaRon
 */

/**
 * Class License Check.
 */
class GF_Tazker_Clickup_License {

	/**
	 * Holds the product name.
	 *
	 * @var string Plugin name to check.
	 */
	private $plugin_name = 'Tazker for ClickUp';

	/**
	 * Holds the domain to check for the license.
	 *
	 * @var string Domain to check for the license.
	 */
	private $license_domain = 'https://dlxplugins.com';

	/**
	 * Holds the license value.
	 *
	 * @var string $license The license value.
	 */
	private $license = '';

	/**
	 * Class constructor.
	 *
	 * @param string $license The site license.
	 */
	public function __construct( string $license = '' ) {
		if ( rgblank( $license ) ) {
			$options = gf_tazker_clickup()::get_options( true );
			$license = rgar( $options, 'license' );
		}
		$this->license = sanitize_text_field( $license );
	}

	/**
	 * Perform a license action and return the result.
	 *
	 * @param string $action   Action to take (check_license, activate_license, deactivate_license).
	 * @param string $license (Optional) License key to process.
	 * @param bool   $force   Whether to skip cache or not.
	 *
	 * @return array $args {
	 *     @bool   $errors        Whether there are errors or not.
	 *     @string $license       License key used.
	 *     @bool   $license_valid Whether the license is valid or not.
	 *     @string $message       Message to display to user.
	 *     @array  $data          Raw response data.
	 *     @string $action        The action that was performed (check_license, activate_license, deactivate_license).
	 * }
	 */
	public function perform_action( string $action, bool $force = true ) {
		$license = sanitize_text_field( $this->license );

		// Perform license action.
		return $this->perform_license_action( $action, $force );
	}

	/**
	 * Perform a license check based on action.
	 *
	 * @param string $action Action to take.
	 * @param bool   $force  Whether to skip any caching.
	 */
	private function perform_license_action( string $action, bool $force ) {
		$options        = gf_tazker_clickup()::get_options( true );
		$maybe_check    = get_site_transient( 'gform_tazker_clickup_license_check' );
		$license_status = rgar( $options, 'license_status' );
		$license        = rgar( $options, 'license' );
		$license_valid  = rgar( $options, 'license_valid' );

		if ( 'check_license' === $action && ! $force && $maybe_check ) {
			return $maybe_check;
		}

		// Set transient for checking.
		if ( rgblank( $this->license ) && 'check_license' === $action ) {
			return array(
				'errors'        => true,
				'license'       => $this->license,
				'license_valid' => false,
				'message'       => __( 'It appears the license key is blank.', 'toggl-plan-gravity-forms' ),
				'data'          => array(),
				'action'        => $action,
			);
		}

		// Check for valid license.
		$store_url  = $this->license_domain;
		$api_params = array(
			'edd_action' => $action,
			'license'    => $this->license,
			'item_name'  => rawurlencode( $this->plugin_name ),
			'url'        => home_url(),
		);
		// Call the custom API.
		$response = wp_remote_post(
			$store_url,
			array(
				'timeout'   => 15,
				'sslverify' => false,
				'body'      => $api_params,
			)
		);

		// If an error, return response.
		if ( is_wp_error( $response ) ) {
			return $response;
		}
		if ( 200 !== wp_remote_retrieve_response_code( $response ) ) {
			return new \WP_Error( 'tazker_clickup_license_communications_error', __( 'We could not communicate with the update server. Please try again later.', 'toggl-plan-gravity-forms' ) );
		}
		// Succeeded, let's check the response.
		$response = $this->get_response( gf_tazker_clickup()->maybe_decode_json( wp_remote_retrieve_body( $response ) ), $action );

		if ( ! rgar( $response, 'errors' ) ) {
			if ( 'deactivate_license' === $action ) {
				// Clear license.
				$options = wp_parse_args(
					array(
						'license'       => '',
						'license_valid' => false,
					),
					$options
				);
			} else {
				$options = wp_parse_args(
					array(
						'license'       => rgar( $response, 'license' ),
						'license_valid' => rgar( $response, 'license_valid' ),
					),
					$options
				);
			}
			delete_site_transient( 'gform_tazker_clickup_license_check' );
			gf_tazker_clickup()::update_options( $options );
		}

		// Add query flag for checking the license so we don't ping the API every time.
		if ( 'check_license' === $action ) {
			set_site_transient( 'gform_tazker_clickup_license_check', $response, 12 * HOUR_IN_SECONDS );
		}

		// Perform an action based on response/action.
		do_action( 'gform_tazker_clickup_license_' . $action, $response );

		// Return any custom data.
		$data = apply_filters( 'gform_tazker_clickup_license_data_' . $action, $response );

		return $data;
	}

	/**
	 * Retrieve response data in array format.
	 *
	 * @param array  $response Raw response data.
	 * @param string $action   Action to take (check_license, activate_license, deactivate_license).
	 *
	 * @return array $args {
	 *     @bool   $errors        Whether there are errors or not.
	 *     @string $license       License key used.
	 *     @bool   $license_valid Whether the license is valid or not.
	 *     @string $message       Message to display to user.
	 *     @array  $data          Raw response data.
	 *     @string $action        The action that was performed (check_license, activate_license, deactivate_license).
	 * }
	 */
	private function get_response( array $response, string $action ) {
		$errors = false;

		$return_defaults = array(
			'errors'        => false,
			'license'       => $this->license,
			'license_valid' => true,
			'message'       => '',
			'data'          => $response,
			'action'        => $action,
		);

		// Format the date.
		if ( rgars( $return_defaults, 'data/expires' ) ) {

			$return_defaults['data']['expires_human_time_diff'] = human_time_diff( time(), strtotime( rgars( $return_defaults, 'data/expires' ) ) );
			$return_defaults['data']['expires'] = date_i18n( 'F jS, Y', strtotime( rgars( $return_defaults, 'data/expires' ) ) );
		}

		if ( true === rgar( $response, 'success' ) ) {
			if ( 'deactivate_license' === $action ) {
				delete_site_transient( 'gform_tazker_clickup_license_check' );
				return wp_parse_args(
					array(
						'message' => __( 'Your license key has been deactivated.', 'toggl-plan-gravity-forms' ),
					),
					$return_defaults
				);
			}
			if ( 'activate_license' === $action || 'check_license' === $action ) {
				return wp_parse_args(
					array(
						'message' => __( 'Your license key is active and valid.', 'toggl-plan-gravity-forms' ),
					),
					$return_defaults
				);
			}
		}

		// There are errors.
		$error_message = __( 'An error occurred, please try again.', 'toggl-plan-gravity-forms' );
		if ( rgar( $response, 'error' ) ) {
			switch ( rgar( $response, 'error' ) ) {
				case 'expired':
					$error_message = sprintf(
						/* Translators: %s is a date format placeholder */
						__( 'Your license key expired on %s.', 'toggl-plan-gravity-forms' ),
						date_i18n( get_option( 'date_format' ), strtotime( $license_data->expires, current_time( 'timestamp' ) ) ) // phpcs:ignore
					);
					break;

				case 'disabled':
				case 'revoked':
					$error_message = __( 'Your license key has been disabled.', 'toggl-plan-gravity-forms' );
					break;

				case 'missing':
					$error_message = __( 'Invalid license.', 'toggl-plan-gravity-forms' );
					break;
				case 'invalid':
				case 'site_inactive':
					$error_message = __( 'Your license is not active for this URL.', 'toggl-plan-gravity-forms' );
					break;

				case 'item_name_mismatch':
					/* Translators: %s is the plugin name */
					$error_message = sprintf( __( 'This appears to be an invalid license key for %s.', 'toggl-plan-gravity-forms' ), 'Toggl Plan for Gravity Forms' );
					break;

				case 'no_activations_left':
					$error_message = __( 'Your license key has reached its activation limit.', 'toggl-plan-gravity-forms' );
					break;
			}
		}

		return wp_parse_args(
			array(
				'errors'        => true,
				'license_valid' => false,
				'message'       => $error_message,
			),
			$return_defaults
		);

	}
}

A license helper class. Feel free to abstract it or customize it for your own use-case.