WordPressのセットアップ(InfoTown_Setup, InfoTown_Head、InfoTown_Admin、InfoTown_Post)クラスのサンプルです。

class-head.php

<?php
/**
 * HEAD処理
 *
 * @package   InfoTown
 * @author    Hiroshi Sawai <info@info-town.jp>
 * @copyright Hiroshi Sawai
 */
class InfoTown_Head {

	/**
	 * Load stylesheets.
	 *
	 * @param array $args arguments of loading style.
	 *
	 * @since 1.0
	 */
	public function load_stylesheets( $args ) {
		add_action(
			'wp_enqueue_scripts',
			function () use ( $args ) {
				foreach ( $args as $arg ) {
					wp_enqueue_style( $arg[0], $arg[1], $arg[2], $arg[3], $arg[4] );
				}
			}
		);
	}

	/**
	 * Load script.
	 *
	 * @param array $args arguments of loading script.
	 *
	 * @since 1.0
	 */
	public function load_scripts( $args ) {
		add_action(
			'wp_enqueue_scripts',
			function () use ( $args ) {
				foreach ( $args as $arg ) {
					wp_enqueue_script( $arg[0], $arg[1], $arg[2], $arg[3], $arg[4] );
				}
			}
		);
	}

	/**
	 * Set viewport in head
	 *
	 * @param string $output view port.
	 *
	 * @since 1.0
	 */
	public function set_viewport( $output ) {
		add_action(
			'wp_head',
			function () use ( $output ) {
				echo "\n" . $output . PHP_EOL;
			}
		);
	}
}

class-setup.php

<?php
/**
 * Set up theme.
 *
 * @package   InfoTown
 * @author    Hiroshi Sawai <info@info-town.jp>
 * @copyright Hiroshi Sawai
 */
class InfoTown_SetUp {

	/**
	 * @var string $domain Text domain
	 */
	public $theme;

	/**
	 * @var string $domain Text domain
	 */
	public $domain;

	/**
	 * @return string テーマ名を返します。
	 */
	public function get_theme() {
		return $this->theme;
	}

	/**
	 * @return bool|string テキストドメイン名を返します。
	 */
	public function get_text_domain() {
		return $this->domain;
	}

	/**
	 * Specify theme name and text domain name.
	 *
	 * 可能文字は半角英数字、アンダースコア、ハイフンのみです(WordPressの仕様とはことなります)。
	 *
	 * @param string $theme  テーマ名です。テーマ名の可能文字は半角英数字、アンダースコア、ハイフンのみです。
	 * @param string $domain テキストドメインです。ドメイン名の可能文字は半角英数字、アンダースコア、ハイフンのみです。
	 */
	function __construct( $theme, $domain = '' ) {
		$this->theme  = $theme;
		$this->domain = $domain || $theme;
	}

	/**
	 * Specify translation file.
	 *
	 * @param string $dir 翻訳ファイルディレクトリです。
	 *                    通常 テーマディレクトリ/languagesです。
	 *
	 * @since 1.0.0
	 */
	public function set_load_domain( $dir ) {
		$dir = $dir || get_template_directory() . '/languages';
		add_action(
			'after_setup_theme',
			function () use ( $dir ) {
				load_theme_textdomain( $this->domain, $dir );
			}
		);
	}

	/**
	 * Set theme supports.
	 *
	 * @param array $args サポートする機能です。
	 *
	 * @since 1.0.0
	 */
	public function set_theme_support( $args ) {
		foreach ( $args as $arg ) {
			add_theme_support( $arg );
		}
	}

	/**
	 * Set post thumbnail(eye catch).
	 *
	 * @param integer $width  アイキャッチ横サイズです。
	 * @param integer $height アイキャッチ縦サイズです。
	 */
	public function set_post_thumbnails( $width = 640, $height = 480 ) {
		add_action(
			'after_setup_theme',
			function () use ( $width, $height ) {
				add_theme_support( 'post-thumbnails' );
				set_post_thumbnail_size( $width, $height );
			}
		);
	}

	/**
	 * Set menu.
	 *
	 * @param array $args メニューの配列です。
	 */
	public function set_menu( $args ) {
		foreach ( $args as $key => $value ) {
			register_nav_menu( $key, __( $value, $this->domain ) );
		}
	}

	/**
	 * Register widget.
	 *
	 * @param array $widgets settings of widgets.
	 *
	 * @since 1.0.0
	 */
	function set_widget( $widgets ) {
		add_action(
			'widgets_init',
			function () use ( $widgets ) {
				foreach ( $widgets as $widget ) {
					register_sidebar( $widget );
				}
			}
		);
	}

	/**
	 * Add custom header to theme support.
	 *
	 * callback of after_setup_theme hook.
	 *
	 * @param array $options Associated array of custom header.
	 *
	 * @since 1.0
	 */
	function set_custom_header( $options ) {
		add_theme_support( 'custom-header' );
		$defaults = [
			'width'             => 1140,
			'height'            => 480,
			'header-text'       => false,
			'header-text-color' => '333333',
			'default-image'     => esc_url( get_stylesheet_directory_uri() . '/images/common/default.jpg' ),
			'random-default'    => false,

		];
		$args     = array_merge( $defaults, $options );
		add_action(
			'after_setup_theme',
			function () use ( $args ) {
				$args = apply_filters( 'custom_header_args', $args );
				if ( function_exists( 'get_custom_header' ) ) {
					add_theme_support( 'custom-header', $args );
				}
			}
		);
	}

	/**
	 * Remove no use functions of wp_head.
	 *
	 * @param array $args 削除対象の配列です。
	 *
	 * @since 1.0.0
	 */
	function set_remove_no_use_wp_head( $args ) {
		add_action(
			'after_setup_theme',
			function () use ( $args ) {
				foreach ( $args as $arg ) {
					remove_action( 'wp_head', $arg );
				}
			}
		);
	}

	/**
	 * Load admin css.
	 *
	 * @param string $name css file for admin editor.
	 */
	public function set_editor_style( $name = 'editor-style.css' ) {
		add_editor_style( $name );
	}
}

functions.php

<?php
/*
 * Set timezone
 */
date_default_timezone_set( 'Asia/Tokyo' );

/*
 * Set constant.
 */
define( 'THEME_NAME', 'my-theme' );
define( 'THEME_TEXT_DOMAIN', 'mytheme' );
define( 'THEME_URL', get_template_directory_uri() );
define( 'THEME_ASSETS_URL', THEME_URL );
define( 'THEME_ASSETS_JS_URL', THEME_ASSETS_URL . '/js' );
define( 'THEME_ASSETS_CSS_URL', THEME_ASSETS_URL . '/css' );
define( 'THEME_CUSTOM_HEADER_WIDTH', 940 );
define( 'THEME_CUSTOM_HEADER_HEIGHT', 330 );
define( 'THEME_EYECATCH_WIDTH', 480 );
define( 'THEME_EYECATCH_HEIGHT', 320 );

/*
 * Set theme configuration.
 */
require_once( get_template_directory() . '/includes/class-setup.php' );
// add action and filter
$setup = new InfoTown_Setup( THEME_NAME, THEME_TEXT_DOMAIN );
// Load text domain.
$setup->set_load_domain( get_template_directory() . '/languages' );
// Set eye catch
$setup->set_post_thumbnails( THEME_EYECATCH_WIDTH, THEME_EYECATCH_HEIGHT );
// Set menu.
$setup->set_menu( [
	'global__nav' => 'Global Menu',
	'product'     => 'Product Menu',
	'footer'      => 'Footer Menu',
] );
// Set editor css.
$setup->set_editor_style();
// Set widget.
$widgets = [
	'front_slider' => [
		'name'          => __( 'トップスライダー画像', THEME_TEXT_DOMAIN ),
		'description'   => __(
			'トップページのスライダー画像を設定します。',
			THEME_TEXT_DOMAIN
		),
		'id'            => 'front_slider',
		'before_widget' => '<div id="%1$s" class="widget %2$s"><div class="widget-inner">',
		'after_widget'  => '</div></div>',
		'before_title'  => '<h4 class="title">',
		'after_title'   => '</h4>',
	],
	'side'         => [
		'name'          => __( 'サイドバー', THEME_TEXT_DOMAIN ),
		'description'   => __(
			'サイドバーウィジェットです。',
			THEME_TEXT_DOMAIN
		),
		'id'            => 'side',
		'before_widget' => '<div id="%1$s" class="widget %2$s"><div class="widget-inner">',
		'after_widget'  => '</div></div>',
		'before_title'  => '<h4 class="title">',
		'after_title'   => '</h4>',
	],
];
$setup->set_widget( $widgets );
// Set custom header.
$setup->set_custom_header( [
	'width'              => THEME_CUSTOM_HEADER_WIDTH,
	'height'             => THEME_CUSTOM_HEADER_HEIGHT,
	'header-text'        => false,
	'default-text-color' => '303030',
	'default-image'      => esc_url( get_stylesheet_directory_uri() . '/images/common/default.jpg' ),
	'random-default'     => false,
] );
// Set theme support.
$supports = [ 'automatic-feed-links', 'title-tag', 'custom-background' ];
$setup->set_theme_support( $supports );
// Remove no use function of wp_head.
$no_use = [ 'wp_generator', 'wlwmanifest_link', 'rsd_link' ];
$setup->set_remove_no_use_wp_head( $no_use );

/*
 * Set header.
 */
require_once( get_template_directory() . '/includes/class-head.php' );
$header = new InfoTown_Head();
// Load stylesheet
$styles = [
	0 => [
		'bootstrap',
		THEME_ASSETS_CSS_URL . '/vendor/bootstrap/css/bootstrap.min.css',
		false,
		'3.3.6',
		'all',
	],
	1 => [
		'font-awesome',
		THEME_ASSETS_CSS_URL . '/vendor/font-awesome/css/font-awesome.min.css',
		false,
		'4.5.0',
		'all',
	],
	2 => [
		'animate',
		THEME_ASSETS_CSS_URL . '/vendor/animate.min.css',
		false,
		'4.5.0',
		'all',
	],
	3 => [
		'scrollbar',
		THEME_ASSETS_JS_URL . '/vendor/malihu-custom-scrollbar-plugin/jquery.mCustomScrollbar.min.css',
		false,
		'3.1.13',
		'all',
	],
	4 => [
		'slick',
		THEME_ASSETS_CSS_URL . '/vendor/slick/slick.css',
		false,
		'1.5.8',
		'all',
	],
	5 => [
		'slick-theme',
		THEME_ASSETS_CSS_URL . '/vendor/slick/slick-theme.css',
		false,
		'1.5.8',
		'all',
	],
	6 => [
		'style',
		get_stylesheet_uri(),
		false,
		'1.0',
		'all',
	],
];
$header->load_stylesheets( $styles );
// Load script.
$scripts = [
	0 => [
		'scrollbar',
		THEME_ASSETS_JS_URL . '/vendor/malihu-custom-scrollbar-plugin/jquery.mCustomScrollbar.concat.min.js',
		[ 'jquery' ],
		'3.1.13',
		false,
	],
	1 => [
		'slick',
		THEME_ASSETS_JS_URL . '/vendor/slick.min.js',
		[ 'jquery' ],
		'1.5.8',
		false,
	],
	2 => [
		'theme',
		THEME_ASSETS_JS_URL . '/theme.min.js',
		[ 'jquery' ],
		'1.0.0',
		false,
	],
];
$header->load_scripts( $scripts );
// Set viewport in head
$header->set_viewport( '<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1" />' );

/*
 * Load utility classes of InfoTown package.
 */
require_once( get_template_directory() . '/inc/utils/class.attachments.php' );
require_once( get_template_directory() . '/inc/utils/class.categories.php' );
require_once( get_template_directory() . '/inc/utils/class.categories-view.php' );
require_once( get_template_directory() . '/inc/utils/class.date.php' );
require_once( get_template_directory() . '/inc/utils/class.device.php' );
require_once( get_template_directory() . '/inc/utils/class.links.php' );
require_once( get_template_directory() . '/inc/utils/class.str.php' );

/*
 * Load short code classes of InfoTown package.
 */
require_once( get_template_directory() . '/inc/shortcode/class.shortcode-images.php' );
require_once( get_template_directory() . '/inc/shortcode/class.shortcode-multibr.php' );
require_once( get_template_directory() . '/inc/shortcode/class.shortcode-bloginfo.php' );
add_shortcode( 'br', [ new InfoTown_Shortcode_Multibr(), 'br' ] );
add_shortcode( 'img', [ new InfoTown_Shortcode_Images(), 'img' ] );
add_shortcode( 'bloginfo', [ new InfoTown_Shortcode_Bloginfo(), 'bloginfo' ] );