protected static function setup_plan_and_form_atts( $plan_id, $atts ) {

		$plan = new LLMS_Access_Plan( $plan_id );

		$atts['plan']    = $plan;
		$atts['product'] = $plan->get_product();
		$atts['is_free'] = $plan->has_free_checkout();

		$atts['form_location'] = 'checkout';
		$atts['form_title']    = llms_get_form_title( $atts['form_location'], array( 'plan' => $plan ) );
		$atts['form_fields']   = self::clean_form_fields( llms_get_form_html( $atts['form_location'], array( 'plan' => $plan ) ) );

		// Add 'redirect' URL hidden field to be used on purchase completion.
		$plan_redirection_url = $plan->get_redirection_url( false );
		if ( $plan_redirection_url ) {
			$atts['form_fields'] .= ( new LLMS_Form_Field(
				array(
					'id'             => 'llms-redirect',
					'name'           => 'redirect',
					'type'           => 'hidden',
					'value'          => $plan_redirection_url,
					'data_store_key' => false,
				)
			) )->get_html();
		}

		return $atts;
	}