functions.php example for WordPress theme

functions.php

<?php
/**
 * Your theme functions and definitions
 *
 * Set up the theme and provides some helper functions, which are used in the
 * theme as custom template tags. Others are attached to action and filter
 * hooks in WordPress to change core functionality.
 *
 * @package WordPress
 * @subpackage yourtheme
 * @version 1.0.0
 * @author  yourfirm ltd. <http://yourfirm.com/>
 * @license https://www.gnu.org/licenses/gpl-3.0.txt GNU/GPLv3
 * @link https://yourtheme.com
 * @since  1.0.0
 */

define( 'YOURTHEME_THEME_VERSION', '1.0.0' );
define( 'YOURTHEME_TEMPPATH', get_template_directory_uri() );
define( 'YOURTHEME_IMAGES', YOURTHEME_TEMPPATH . '/images' );
define( 'YOURTHEME_TEMPDIR', get_template_directory() );

add_action( 'after_setup_theme', 'yourtheme_theme_setup' );
if ( ! function_exists( 'yourtheme_theme_setup' ) ) {
	/**
	 * Sets up theme defaults and registers support for various WordPress features.
	 *
	 * Note that this function is hooked into the after_setup_theme hook, which
	 * runs before the init hook. The init hook is too late for some features, such
	 * as indicating support for post thumbnails.
	 *
	 * @since  1.0.0
	 */
	function yourtheme_theme_setup() {
		load_theme_textdomain( 'yourtheme', YOURTHEME_TEMPDIR . '/languages' );
		$grid_width = get_theme_mod( 'grid_width', '' );
		if ( ! isset( $content_width ) ) {
			$content_width = $grid_width;
		}

		add_theme_support( 'automatic-feed-links' );
		add_theme_support( 'title-tag' );
		add_theme_support( 'post-thumbnails' );
		add_theme_support( 'post-formats', array( 'aside', 'gallery', 'link', 'image', 'quote', 'status', 'video', 'audio', 'chat' ) );
		add_theme_support( 'html5', array( 'comment-list', 'comment-form', 'search-form', 'gallery', 'caption' ) );
		add_post_type_support( 'page', 'excerpt' );
		add_filter( 'the_content_more_link', 'yourtheme_remove_more_link_scroll_wrap' );

		/********* Menus ***********/
		add_action( 'init', 'yourtheme_register_my_menus' );
		require_once( YOURTHEME_TEMPDIR . '/inc/menu-walker.php' );

		/********* Enqueue Scripts ***********/
		add_action( 'wp_enqueue_scripts', 'yourtheme_frontend_scripts' );
		add_action( 'admin_enqueue_scripts', 'yourtheme_backend_scripts' );

		/********* Register sidebars ***********/
		require_once( YOURTHEME_TEMPDIR . '/inc/sidebars.php' );

		/********* Breadcrumbs! ***********/
		require_once( YOURTHEME_TEMPDIR . '/inc/breadcrumbs.php' );

		/********* Additional fields in page and post editor ***********/
		require_once( YOURTHEME_TEMPDIR . '/inc/admin/page-additional-fields.php' );
		require_once( YOURTHEME_TEMPDIR . '/inc/admin/post-additional-fields.php' );

		/********* Additional fields in categories ***********/
		require_once( YOURTHEME_TEMPDIR . '/inc/admin/categories-additional-fields.php' );

	}
}

/********* Theme Customizer ***********/
require_once( YOURTHEME_TEMPDIR . '/inc/customizer/customizer.php' );
/********* Theme Settings ***********/
require_once( YOURTHEME_TEMPDIR . '/inc/theme-settings/theme-settings.php' );

if ( ! function_exists( 'yourtheme_register_my_menus' ) ) {
	/**
	 * Register menu function
	 *
	 * Registers new menu locations based on theme option settings.
	 *
	 * @since  1.0.0
	 */
	function yourtheme_register_my_menus() {
		register_nav_menus( array(
			'header-menu' => esc_html__( 'Header Menu', 'yourtheme' ),
			'footer-menu' => esc_html__( 'Footer Menu', 'yourtheme' ),
		) );
	}
}

/********* Additional Includes ***********/
if ( in_array( 'woocommerce/woocommerce.php', get_option( 'active_plugins' ), true ) ) {
	include_once( get_stylesheet_directory() . '/inc/woocommerce-custom.php' );
}

if ( ! function_exists( 'yourtheme_frontend_scripts' ) ) {
	/**
	 * Enqueue scripts and styles.
	 *
	 * @since 1.0.0
	 */
	function yourtheme_frontend_scripts() {

		wp_enqueue_style( 'yourtheme_main_css', get_stylesheet_uri(), array( 'wp-mediaelement' ) );

		// Styles from options - appends styles to $custom_css variable.
		$yourtheme_settings = get_option( 'yourtheme_settings', '' );
		if ( isset( $yourtheme_settings->settings->google_maps_enable ) && '1' === $yourtheme_settings->settings->google_maps_enable ) {
			if ( '' !== $yourtheme_settings->settings->google_api_key ) {
				wp_enqueue_script( 'google_maps_api', 'https://maps.googleapis.com/maps/api/js?key=' . $yourtheme_settings->settings->google_api_key . '&v=3', '', '', true );
			} else {
				wp_enqueue_script( 'google_maps_api', '//maps.googleapis.com/maps/api/js?v=3', '', '', true );
			}

			wp_enqueue_script( 'google_maps_style', YOURTHEME_TEMPPATH . '/js/google-maps-style.js', array( 'jquery' ), '', true );
		}

		wp_enqueue_script( 'yourtheme_custom', YOURTHEME_TEMPPATH . '/js/custom.js', array( 'jquery', 'wp-mediaelement' ),'', true );

	}
}

if ( ! function_exists( 'yourtheme_backend_scripts' ) ) {
	/**
	 * Enqueue bac kend scripts and styles.
	 *
	 * @param  string $hook Hook string to check the page, so that not all scripts are loaded
	 *                      unnecessarily on every page.
	 * @since 1.0.0
	 */
	function yourtheme_backend_scripts( $hook ) {
		wp_enqueue_style( 'yourtheme_admin_style', YOURTHEME_TEMPPATH . '/css/admin.css' );
		wp_enqueue_style( 'wp-color-picker' );

		wp_enqueue_media();
		wp_enqueue_script( 'wp-color-picker' );
		wp_enqueue_script( 'yourtheme_category_image_upload', YOURTHEME_TEMPPATH . '/js/admin.js' );

		if ( is_singular() ) {
			wp_enqueue_script( 'comment-reply' );
		}
	}
}

if ( ! function_exists( 'yourtheme_fonts_url' ) ) {
	/**
	 * Register Google fonts
	 *
	 * @since 1.0.0
	 * @return string Google fonts URL for the theme.
	 */
	function yourtheme_fonts_url() {
		$fonts_url = '';

		$ubuntu   = esc_html_x( 'on', 'Ubuntu font: on or off', 'yourtheme' );
		$vollkorn = esc_html_x( 'on', 'Vollkorn font: on or off', 'yourtheme' );
		$roboto   = esc_html_x( 'on', 'Roboto font: on or off', 'yourtheme' );

		/*
		 * Translators: If there are characters in your language that are not supported
		 * by Ubuntu, Vollkorn or Roboto, translate this to 'off'. Do not translate into your own language.
		 */
		if ( 'off' !== $ubuntu || 'off' !== $vollkorn || 'off' !== $roboto ) {
			$font_families = array();

			if ( 'off' !== $ubuntu ) {
				$font_families[] = 'Ubuntu:300';
			}

			if ( 'off' !== $vollkorn ) {
				$font_families[] = 'Vollkorn:400italic';
			}

			if ( 'off' !== $roboto ) {
				$font_families[] = 'Roboto Condensed:700';
			}

			$query_args = array(
				'family' => rawurlencode( implode( '|', $font_families ) ),
			);

			$fonts_url = add_query_arg( $query_args, 'https://fonts.googleapis.com/css' );
		}

		return esc_url_raw( $fonts_url );
	}
}

/**
 * Sanitization Functions
 *
 * These functions are used for Customizer sanitization.
 */
if ( ! function_exists( 'yourtheme_allowed_tags' ) ) {
	/**
	 * Allowed tags function for wp_kses()
	 *
	 * @return array Array of allowed HTML tags
	 * @since 1.0.0
	 */
	function yourtheme_allowed_tags() {
		return array(
			'a' => array(
				'href' => array(),
				'title' => array(),
			),
			'br' => array(),
			'span' => array(
				'class' => array(),
			),
			'em' => array(),
			'ul' => array(),
			'ol' => array(),
			'li' => array(),
			'strong' => array(),
			'pre' => array(),
			'code' => array(),
			'blockquote' => array(
				'cite' => true,
			),
			'i' => array(
				'class' => array(),
			),
			'cite' => array(
				'title' => array(),
			),
			'abbr' => array(
				'title' => true,
			),
			'select' => array(
				'id'   => array(),
				'name' => array(),
			),
			'option' => array(
				'value' => array(),
			),
		);
	}
}

if ( ! function_exists( 'yourtheme_text_sanitization' ) ) {
	/**
	 * Text sanitization function for Customize API
	 *
	 * @param  string $input Input to be sanitized.
	 * @return string        Sanitized input.
	 * @since 1.0.0
	 */
	function yourtheme_text_sanitization( $input ) {
		return wp_kses_post( force_balance_tags( $input ) );
	}
}

if ( ! function_exists( 'yourtheme_checkbox_sanitization' ) ) {
	/**
	 * Checkbox sanitization function for Customize API
	 *
	 * @param  string $input Checkbox value.
	 * @return integer       Sanitized value.
	 * @since 1.0.0
	 */
	function yourtheme_checkbox_sanitization( $input ) {
		if ( '1' === $input ) {
			return 1;
		} else {
			return '';
		}
	}
}

if ( ! function_exists( 'yourtheme_sanitize_integer' ) ) {
	/**
	 * Integer sanitization function for Customize API
	 *
	 * @param  string $input Input value to check.
	 * @return integer        Returned integer value.
	 * @since 1.0.0
	 */
	function yourtheme_sanitize_integer( $input ) {
		if ( is_numeric( $input ) ) {
			return intval( $input );
		}
	}
}

if ( ! function_exists( 'yourtheme_get_the_widget' ) ) {
	/**
	 * Widget render function - used for showing widgets in the menus
	 *
	 * The widgets don't usually appear in the menu, and the only way to display it
	 * is to save the output of the_widget() function to the buffer and then output it.
	 *
	 * @param  string $widget   The widget's PHP class name.
	 * @param  string $instance The widget's instance settings. Either array or query-style string.
	 * @param  string $args     The widget's sidebar args. Either array or query-style string.
	 * @return string           Widget that is saved in the output buffer.
	 * @since 1.0.0
	 */
	function yourtheme_get_the_widget( $widget, $instance = '', $args = '' ) {
		ob_start();
		the_widget( $widget, $instance, $args );
		return ob_get_clean();
	}
}

if ( ! function_exists( 'yourtheme_get_theme_mod_not_empty' ) ) {
	/**
	 * Get theme modification if it is empty
	 *
	 * @param  string $option  Theme modification name.
	 * @param  [type] $default The default value of theme modification.
	 * @return [type]          Returns the default value if there is nothing set.
	 * @since 1.0.0
	 */
	function yourtheme_get_theme_mod_not_empty( $option, $default ) {
		$return = get_theme_mod( $option, $default );
		if ( '' === $return ) {
			$return = $default;
		}
		return $return;
	}
}