settings.php

<?php
/**
 * Generated by the WordPress Option Page generator
 * at http://jeremyhixon.com/wp-tools/option-page/
 */

$pllx_options_original = [
	'feature_translate_cat_in_menus' => 'true',
	'feature_replace_front_page' => 'true',
	'feature_category_featured_post' => 'true',
	'feature_remove_duplicate_posts' => 'false',
	'language_behaviour' =>  'browser',
	'forced_languages' => '',
	'use_current_language' => 'false',
	'custom_post_types' => 'post,page',
];

$pllx_options_recommended = [
	'feature_translate_cat_in_menus' => 'false',
	'feature_replace_front_page' => 'true',
	'feature_category_featured_post' => 'true',
	'feature_remove_duplicate_posts' => 'true',
	'language_behaviour' =>  'all',
	'forced_languages' => 'en',
	'use_current_language' => 'true',
	'custom_post_types' => 'post,page',
];

$pllx_options_defaults = $pllx_options_recommended;
//$pllx_options_defaults = $pllx_options_original;

/* 
 * Retrieve this value with:
 * $language_mix_options = get_option( 'language_mix_option_name' ); // Array of All Options
 * $language_behaviour = $language_mix_options['language_behaviour']; // Language behavior
 * $forced_languages = $language_mix_options['forced_languages']; // Forced languages
 * $use_current_language = $language_mix_options['use_current_language']; // Use current language
 * $custom_post_types = $language_mix_options['custom_post_types']; // Custom post types
 */


class LanguageMix {
	private $language_mix_options;

	public function __construct() {
		add_action( 'admin_menu', array( $this, 'language_mix_add_plugin_page' ) );
		add_action( 'admin_init', array( $this, 'language_mix_page_init' ) );
	}

	public function language_mix_add_plugin_page() {
		add_options_page(
			__('Language Mix', 'language-mix'), // page_title
			__('Language Mix', 'language-mix'), // menu_title
			'manage_options', // capability
			'language-mix', // menu_slug
			array( $this, 'language_mix_create_admin_page' ) // function
		);
	}


	public function language_mix_create_admin_page() {
		
		$this->language_mix_options = get_option( 'language_mix_option_name' ); ?>

		<div class="wrap">
			<h2>Language Mix</h2>
			<p></p>
			<?php settings_errors(); ?>
			<form method="post" action="options.php">
				<?php
					settings_fields( 'language_mix_option_group' );
					do_settings_sections( 'language-mix-admin' );
					submit_button();
				?>
			</form>
		</div>
	<?php }

	public function language_mix_page_init() {
		global $pllx_options_defaults;

		register_setting(
			'language_mix_option_group', // option_group
			'language_mix_option_name', // option_name
            [
                'sanitize_callback' => array( $this, 'language_mix_sanitize' ), 
                'default' => $pllx_options_defaults,
            ]
		);

		add_settings_section(
			'language_mix_setting_section', // id
			__('Settings', 'language-mix'), // title
			array( $this, 'language_mix_section_info' ), // callback
			'language-mix-admin' // page
		);

		add_settings_field(
			'feature_translate_cat_in_menus', // id
			__('Translate categories in menus', 'language-mix'), // title
			array( $this, 'feature_translate_cat_in_menus_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'feature_replace_front_page', // id
			__('Replacing front page', 'language-mix'), // title
			array( $this, 'feature_replace_front_page_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'feature_category_featured_post', // id
			__('Category featured post', 'language-mix'), // title
			array( $this, 'feature_category_featured_post_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'feature_remove_duplicate_posts', // id
			__('Hide redundant translations', 'language-mix'), // title
			array( $this, 'feature_remove_duplicate_posts_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'language_behaviour', // id
			__('Language behavior', 'language-mix'), // title
			array( $this, 'language_behaviour_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'forced_languages', // id
			__('Forced languages', 'language-mix'), // title
			array( $this, 'forced_languages_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'use_current_language', // id
			__('Use current language', 'language-mix'), // title
			array( $this, 'use_current_language_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

		add_settings_field(
			'custom_post_types', // id
			__('Custom post types', 'language-mix'), // title
			array( $this, 'custom_post_types_callback' ), // callback
			'language-mix-admin', // page
			'language_mix_setting_section' // section
		);

	}

	public function language_mix_sanitize($input) {
		$sanitary_values = array();
		if ( isset( $input['language_behaviour'] ) ) {
			$sanitary_values['language_behaviour'] = $input['language_behaviour'];
		}

		if ( isset( $input['forced_languages'] ) ) {
			$sanitary_values['forced_languages'] = sanitize_text_field( $input['forced_languages'] );
		}

		if ( isset( $input['use_current_language'] ) ) {
			$sanitary_values['use_current_language'] = $input['use_current_language'];
		}

		if ( isset( $input['custom_post_types'] ) ) {
			$sanitary_values['custom_post_types'] = sanitize_text_field( $input['custom_post_types'] );
		}
		
		if ( isset( $input['feature_translate_cat_in_menus'] ) ) {
			$sanitary_values['feature_translate_cat_in_menus'] = sanitize_text_field( $input['feature_translate_cat_in_menus'] );
		}

		if ( isset( $input['feature_replace_front_page'] ) ) {
			$sanitary_values['feature_replace_front_page'] = sanitize_text_field( $input['feature_replace_front_page'] );
		}

		if ( isset( $input['feature_category_featured_post'] ) ) {
			$sanitary_values['feature_category_featured_post'] = sanitize_text_field( $input['feature_category_featured_post'] );
		}

		if ( isset( $input['feature_remove_duplicate_posts'] ) ) {
			$sanitary_values['feature_remove_duplicate_posts'] = sanitize_text_field( $input['feature_remove_duplicate_posts'] );
		}

		return $sanitary_values;
	}

	public function language_mix_section_info() {
		global $pllx_options_defaults;
		global $pllx_options_original;
		global $pllx_options_recommended;

		?>
		<script type="text/javascript" >
		function pllx_set_defaults(defaults) {
			Object.keys(defaults).forEach(function(key) {
				if (jQuery('#'+key).is(':checkbox')) {
					jQuery('#'+key).prop('checked', (defaults[key] ==='true') );
				} else {
					jQuery('#'+key).val(defaults[key]);
				}
			});
		}
		</script>
		<a href="#" class="button" onclick='javascript: pllx_set_defaults(<?php echo json_encode($pllx_options_defaults) ?>);'>
			<?php echo __('Reset to default', 'language-mix'); ?></a>
		<a href="#" class="button" onclick='javascript: pllx_set_defaults(<?php echo json_encode($pllx_options_original) ?>);'>
			<?php echo __('Set to original settings', 'language-mix'); ?></a>
		<a href="#" class="button" onclick='javascript: pllx_set_defaults(<?php echo json_encode($pllx_options_recommended) ?>);'>
			<?php echo __('Set to recommended settings', 'language-mix'); ?></a>
		<?php
	}

	public function language_behaviour_callback() {
		?> <fieldset><?php $checked = ( isset( $this->language_mix_options['language_behaviour'] ) && $this->language_mix_options['language_behaviour'] === 'all' ) ? 'checked' : '' ; ?>
		<label for="language_behaviour-0"><input type="radio" name="language_mix_option_name[language_behaviour]" id="language_behaviour-0" value="all" <?php echo $checked; ?>> <?php echo __('All languages', 'language-mix'); ?></label><br>
		<?php $checked = ( isset( $this->language_mix_options['language_behaviour'] ) && $this->language_mix_options['language_behaviour'] === 'browser' ) ? 'checked' : '' ; ?>
		<label for="language_behaviour-1"><input type="radio" name="language_mix_option_name[language_behaviour]" id="language_behaviour-1" value="browser" <?php echo $checked; ?>> <?php echo __('Only the languages allowed by the browser', 'language-mix'); ?></label><br>
		<?php $checked = ( isset( $this->language_mix_options['language_behaviour'] ) && $this->language_mix_options['language_behaviour'] === 'override' ) ? 'checked' : '' ; ?>
		<label for="language_behaviour-2"><input type="radio" name="language_mix_option_name[language_behaviour]" id="language_behaviour-2" value="override" <?php echo $checked; ?>> <?php echo __('The languages allowed by the browser plus the ones that are forced', 'language-mix'); ?></label></fieldset> <?php
	}

	public function forced_languages_callback() {
		printf(
			'<input class="regular-text" type="text" name="language_mix_option_name[forced_languages]" id="forced_languages" value="%s">',
			isset( $this->language_mix_options['forced_languages'] ) ? esc_attr( $this->language_mix_options['forced_languages']) : ''
		);
	}

	public function use_current_language_callback() {
		printf(
			'<input type="checkbox" name="language_mix_option_name[use_current_language]" id="use_current_language" value="true" %s> <label for="use_current_language">' . __('Allow always the current language with higher priority', 'language-mix') . '</label>',
			( isset( $this->language_mix_options['use_current_language'] ) && $this->language_mix_options['use_current_language'] === 'true' ) ? 'checked' : ''
		);
	}

	public function custom_post_types_callback() {
		printf(
			'<input class="regular-text" type="text" name="language_mix_option_name[custom_post_types]" id="custom_post_types" value="%s">',
			isset( $this->language_mix_options['custom_post_types'] ) ? esc_attr( $this->language_mix_options['custom_post_types']) : ''
		);
	}

	public function feature_translate_cat_in_menus_callback() {
		printf(
			'<input type="checkbox" name="language_mix_option_name[feature_translate_cat_in_menus]" id="feature_translate_cat_in_menus" value="true" %s> <label for="feature_translate_cat_in_menus">' . __('Enable translating categories in menu according to the most wanted language', 'language-mix') . '</label>',
			( isset( $this->language_mix_options['feature_translate_cat_in_menus'] ) && $this->language_mix_options['feature_translate_cat_in_menus'] === 'true' ) ? 'checked' : ''
		);
	}

	public function feature_category_featured_post_callback() {
		printf(
			'<input type="checkbox" name="language_mix_option_name[feature_category_featured_post]" id="feature_category_featured_post" value="true" %s> <label for="feature_category_featured_post">' . __('Enable replacing translation for featured post of a category', 'language-mix') . '</label>',
			( isset( $this->language_mix_options['feature_category_featured_post'] ) && $this->language_mix_options['feature_category_featured_post'] === 'true' ) ? 'checked' : ''
		);
	}

	public function feature_replace_front_page_callback() {
		printf(
			'<input type="checkbox" name="language_mix_option_name[feature_replace_front_page]" id="feature_replace_front_page" value="true" %s> <label for="feature_replace_front_page">' . __('Enable replacing the front page by the most wanted language translation.', 'language-mix') . '</label>',
			( isset( $this->language_mix_options['feature_replace_front_page'] ) && $this->language_mix_options['feature_replace_front_page'] === 'true' ) ? 'checked' : ''
		);
	}

	public function feature_remove_duplicate_posts_callback() {
		printf(
			'<input type="checkbox" name="language_mix_option_name[feature_remove_duplicate_posts]" id="feature_remove_duplicate_posts" value="true" %s> <label for="feature_remove_duplicate_posts">' . __('Enable hiding other translations than the most wanted one for a post, thus avoiding duplicate contents.', 'language-mix') . '</label>',
			( isset( $this->language_mix_options['feature_remove_duplicate_posts'] ) && $this->language_mix_options['feature_remove_duplicate_posts'] === 'true' ) ? 'checked' : ''
		);
	}

}
if ( is_admin() )
	$language_mix = new LanguageMix();