Set correct language for ACF options pages with custom post_id

acf-sample-options.php

<?php

class ACF_SampleOptions_Page {

	static $slug = 'sample_options_slug';

	static $post_id = 'sample_options_id';

	public static function init() {

//		This sets the options page `post_id` to the correct value based on the current language
		if ( defined( 'ICL_LANGUAGE_CODE' ) && ICL_LANGUAGE_CODE !== 'en' ) {
			self::$post_id .= '_' . ICL_LANGUAGE_CODE;
		}

		if ( function_exists( 'acf_add_local_field_group' ) ) {

			acf_add_local_field_group( array(
				'key'        => self::$slug,
				'title'      => __( 'Sample Options', 'rmg' ),
				'fields'     => array(
					[

						'key' => self::$slug . 'samplefield1',
						'label' => __( 'Basic Text Field', 'textdomain' ),
						'name' => 'sample_field_1',
						'type' => 'text',
						'instructions' => '',
					],
					[

						'key' => self::$slug . 'samplefield2',
						'label' => __( 'Basic Text Field', 'textdomain' ),
						'name' => 'sample_field_2',
						'type' => 'text',
						'instructions' => '',
					],
					[

						'key' => self::$slug . 'samplefield3',
						'label' => __( 'Basic Text Field', 'textdomain' ),
						'name' => 'sample_field_3',
						'type' => 'text',
						'instructions' => '',
					],
				),
				'location'   => array(
					array(
						array(
							'param'    => 'options_page',
							'operator' => '==',
							'value'    => self::$slug,
							'order_no' => 0,
							'group_no' => 0,
						),
					),
				),
				'options'    => array(
					'position'       => 'normal',
					'layout'         => 'default',
					'hide_on_screen' => array(),
				),
				'menu_order' => 0,
			) );


		}

		if ( function_exists( 'acf_add_options_sub_page' ) ) {

			acf_add_options_sub_page( array(
				'menu_title'  => 'Sample Options',
				'menu_slug'   => self::$slug,
				'post_id' => self::$post_id,
				'parent_slug' => 'edit.php?post_type=page'
			) );

		}

	}


}

add_action( 'acf/init', [ 'ACF_SampleOptions_Page', 'init' ] );

// To retrieve the value from ACF you can use a call like this:

$field_value = get_field( 'sample_field_1', ACF_SampleOptions_Page::$post_id );