WordPress_generic_options_page_AJ_Clarke_modified

<?php
/*
	Based on AJ Clarke, "How to Create a Simple WordPress Theme Options Page," WPExplorer,
		November 21, 2016, https://www.wpexplorer.com/wordpress-theme-options/
		
	I started with AJ's code. Like many other examples of creating a theme-options page,
	AJ sometimes used the same string for more than one distinct purpose, creating some
	ambiguity about what role each occurrence of a string plays in its context.
	
	To address this, I've modified the code to use a unique string for each distinct role.
	This allows one to (a) understand better what's going on and (b) modify the string for
	a particular role with a global search/replace without affecting the strings used for
	any other roles.
	
	For example, AJ had:
	
		register_setting( 'theme_options', 'theme_options', array( 'WPEX_Theme_Options', 'sanitize' ) );
		
	where the same string ('theme_options') is used for both of the first two arguments,
	which have distinct meanings:
		argument #1:	$option_group:	"A settings group name. This must match the group name used in register_setting(),
							which is the page slug name on which the form is to appear."
							<https://codex.wordpress.org/Settings_API>
		argument #2: $option_name:	The name of an option to sanitize and save.
	
	A similar remarks applies to the first two arguments of add_menu_page().
	
	I also changed the names of some of the functions/methods defined within the class to more
	obviously signal that these are not standard-WordPress functions. (E.g., I changed the name of
	register_settings(), to distinguish it from the standard-WordPress function register_setting().)
	
	AJ's code used "WPEX_" as a prefix, corresponding to WPExplorer. I changed the prefix to "zzyzx"
	to be more generic and a good candidate for global search/replace.
	
 *
 */
 
 /*	Some WordPress functions have an argument for a callable function. While a PHP function
 	can be passed by its name as a string, "A method of an instantiated object is passed
 	as an array containing an object at index 0 and the method name at index 1."
	See <https://www.php.net/manual/en/language.types.callable.php>.
	
	This structure/syntax is used below.
*/

 /*
	Jim's notes

	<div class="wrap"> apparently matches the look and feel of existing WordPress options pages.
	See Codex, "Creating Options Pages," <https://codex.wordpress.org/Creating_Options_Pages>
	
	zzyzx_Theme_Options_Class					: class
	zzyzx-custom-admin-screen-background-section: CSS class
	zzyzx-custom-admin-login-table				: CSS class
	zzyzx_add_admin_menu						: method		Add sub menu page
	zzyzx_register_settings						: method		Register a setting and its sanitization callback
	zzyzx_get_theme_option						: method		Returns single theme option
	zzyzx_get_theme_option_array				: method		Returns all theme options
	zzyzx_sanitize								: method		Sanitization callback
	zzyzx_create_admin_page						: method		Settings page output
	'zzyzx_theme_options_array'					: id in database for array of theme options
	'zzyzx_theme_options_group'					: id of options group. Should match between
												  (a) first argument of register_setting and
												  (b) argument of settings_fields
	'zzyzx-theme-settings-menu-slug'			: slug name to refer to menu. Should be
												  unique for this menu page and only include
												  lowercase-alpha, dashes, and underscores
	'text-domain'
	zzyzx_get_this_theme_option					: method		Helper function to use in
																your theme to return a
																theme option value

*/

// Exit if accessed directly
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// Start Class
if ( ! class_exists( 'zzyzx_Theme_Options_Class' ) ) {
	class zzyzx_Theme_Options_Class {
		/*	Start things up */
		public function __construct() {
			// We only need to register the admin panel on the back-end
			if ( is_admin() ) {
				add_action( 'admin_menu', array( 'zzyzx_Theme_Options_Class', 'zzyzx_add_admin_menu' ) );
				add_action( 'admin_init', array( 'zzyzx_Theme_Options_Class', 'zzyzx_register_settings' ) );
			}
		}

		/*	Returns all theme options */
		public static function zzyzx_get_theme_option_array() {
			return get_option( 'zzyzx_theme_options_array' );
		}

		/* Returns single theme option */
		public static function zzyzx_get_theme_option( $name_of_particular_option ) {
			$options = self::zzyzx_get_theme_option_array();
			if ( isset( $options[$name_of_particular_option] ) ) {
				return $options[$name_of_particular_option];
			}
		}

		/*	Adds a top-level menu page */
		public static function zzyzx_add_admin_menu() {
//			add_menu_page() adds a top-level menu page
			add_menu_page(
//				Note: argument is browser-window title, not the <h1> header 
				esc_html__( 'Zzyzx Theme Page Browser Window Title', 'text-domain' ),
//				Note: argument is label that appears in the admin sidebar, clicking on
//				which opens the options page 
				esc_html__( 'Zzyzx Theme Menu Label', 'text-domain' ),
				'manage_options', // Capability required in order to see this menu
				'zzyzx-theme-settings-menu-slug', // slug for resultant options page
//				Callable function to be called to output the content of the page.
//				See note at top about a method being passed as an array
				array( 'zzyzx_Theme_Options_Class', 'zzyzx_create_admin_page' )
			);
		}

		/**
		 * Register a setting and its sanitization callback.
		 *
		 * We are only registering 1 setting so we can store all options in a single option as
		 * an array. You could, however, register a new setting for each option
		 */
		public static function zzyzx_register_settings() {
			register_setting(
				'zzyzx_theme_options_group',
				'zzyzx_theme_options_array',
//				Notes:
//				(1) See note at top about a method being passed as an array
//				(2) The third argument of register_setting() is $args, an array of "Data
//					used to describe the setting when registered." Although I don't understand
//					perfectly how the following jibes with the documentation, it seems
//					to be OK to just pass a callable function in that argument.
				array( 'zzyzx_Theme_Options_Class', 'zzyzx_sanitize' )
			);
		}

		/**
		 * Sanitization callback
		 */
		public static function zzyzx_sanitize( $options ) {

			// If we have options let's sanitize them
			if ( $options ) {

				// Checkbox
				if ( ! empty( $options['checkbox_example'] ) ) {
					$options['checkbox_example'] = 'on';
				} else {
					// Remove from options if not checked
					unset( $options['checkbox_example'] ); 
				}

				// Input
				if ( ! empty( $options['input_example'] ) ) {
					$options['input_example'] = sanitize_text_field( $options['input_example'] );
				} else {
					unset( $options['input_example'] ); // Remove from options if empty
				}

				// Select
				if ( ! empty( $options['select_example'] ) ) {
					$options['select_example'] = sanitize_text_field( $options['select_example'] );
				}
			}
			// Return sanitized options
			return $options;
		}

		/*	Outputs the settings page */
		public static function zzyzx_create_admin_page() { ?>
			<div class="wrap"> <!--matches the look and feel of existing WordPress options pages-->
				<h1><?php esc_html_e( 'Zzyzx Theme Options Page header', 'text-domain' ); ?></h1>
				<form method="post" action="options.php">
					<?php
						// settings_fields() outputs nonce, action, and option_page fields for a settings page
						// Argument should match the group name used in register_setting()
						settings_fields( 'zzyzx_theme_options_group' );
					?>
					<table class="form-table zzyzx-custom-admin-login-table">
						<?php // Checkbox example ?>
						<tr valign="top">
							<th scope="row"><?php esc_html_e( 'Checkbox Example Label', 'text-domain' ); ?></th>
							<td>
								<?php $value = self::zzyzx_get_theme_option( 'checkbox_example' ); ?>
								<input type="checkbox" name="zzyzx_theme_options_array[checkbox_example]"<?php checked( $value, 'on' ); ?>>
									<?php esc_html_e( 'Checkbox example description.', 'text-domain' ); ?>
							</td>
						</tr>

						<?php // Text input example ?>
						<tr valign="top">
							<th scope="row"><?php esc_html_e( 'Input Example Label', 'text-domain' ); ?></th>
							<td>
								<?php $value = self::zzyzx_get_theme_option( 'input_example' ); ?>
								<input type="text" name="zzyzx_theme_options_array[input_example]" value="<?php echo esc_attr( $value ); ?>">
							</td>
						</tr>

						<?php // Select example ?>
						<tr valign="top" class="zzyzx-custom-admin-screen-background-section">
							<th scope="row"><?php esc_html_e( 'Select Example Label', 'text-domain' ); ?></th>
							<td>
								<?php $value = self::zzyzx_get_theme_option( 'select_example' ); ?>
								<select name="zzyzx_theme_options_array[select_example]">
									<?php
									$options = array(
										'1' => esc_html__( 'Option 1', 'text-domain' ),
										'2' => esc_html__( 'Option 2', 'text-domain' ),
										'3' => esc_html__( 'Option 3', 'text-domain' ),
									);
									foreach ( $options as $id => $label ) { ?>
										<option value="<?php echo esc_attr( $id ); ?>" <?php selected( $value, $id, true ); ?>>
											<?php echo strip_tags( $label ); ?>
										</option>
									<?php } ?>
								</select>
							</td>
						</tr>

					</table>

					<?php submit_button(); ?>

				</form>

			</div><!-- .wrap -->
		<?php }

	}
}
new zzyzx_Theme_Options_Class();

// Helper function to use in your theme to return a theme option value
function zzyzx_get_this_theme_option( $name_of_particular_option = '' ) {
	return zzyzx_Theme_Options_Class::zzyzx_get_theme_option( $name_of_particular_option );
}