Sample functions.php

functions.php

<?php

// remove API access
// https://developer.wordpress.org/rest-api/using-the-rest-api/frequently-asked-questions/
add_filter( 'rest_authentication_errors', function( $result ) {
    if ( ! empty( $result ) ) {
        return $result;
    }
    if ( ! is_user_logged_in() ) {
        return new WP_Error( 'rest_not_logged_in', 'You are not currently logged in.', array( 'status' => 401 ) );
    }
    return $result;
});

// Disable xmlrpc

add_filter( 'xmlrpc_enabled', '__return_false' );
remove_action( 'wp_head', 'rsd_link' );

// Remove Divi calls to Google fonts API
function remove_google_fonts() {
	wp_dequeue_style( 'divi-fonts' );
	wp_dequeue_style( 'et-gf-open-sans' );
} add_action( 'wp_enqueue_scripts', 'remove_google_fonts', 20 );

// Remove dashicons from frontend
function wpdocs_dequeue_dashicon() {
    if (current_user_can( 'update_core' )) {
        return;
    }
    wp_deregister_style('dashicons');
} add_action( 'wp_enqueue_scripts', 'wpdocs_dequeue_dashicon' );

// Enqueue activelink.js only on mission examples page
function conditional_enqueue_stuff() {
	if ( is_page( 'mission-examples' ) ) {
		wp_enqueue_script('active-link', get_stylesheet_directory_uri() . '/js/activelink.js', array(), FALSE, TRUE);
	}
} add_action( 'wp_enqueue_scripts', 'conditional_enqueue_stuff' );

// enable divi functions
function my_enqueue_assets() {
	wp_enqueue_style( 'parent-style', get_template_directory_uri().'/style.css' );
	wp_enqueue_script('jquery-sticky', get_stylesheet_directory_uri() . '/js/theia-sticky-sidebar.min.js', array(), FALSE, TRUE);
} add_action( 'wp_enqueue_scripts', 'my_enqueue_assets' );

/**
 * Disable the emoji's
 */
function disable_emojis() {
	remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
	remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
	remove_action( 'wp_print_styles', 'print_emoji_styles' );
	remove_action( 'admin_print_styles', 'print_emoji_styles' );   
	remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
	remove_filter( 'comment_text_rss', 'wp_staticize_emoji' );     
	remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );
	add_filter( 'tiny_mce_plugins', 'disable_emojis_tinymce' );
	add_filter( 'wp_resource_hints', 'disable_emojis_remove_dns_prefetch', 10, 2 );
} add_action( 'init', 'disable_emojis' );

/**
* Filter function used to remove the tinymce emoji plugin.
*
* @param    array  $plugins 
* @return   array             Difference betwen the two arrays
*/
function disable_emojis_tinymce( $plugins ) {
	if ( is_array( $plugins ) ) {
		return array_diff( $plugins, array( 'wpemoji' ) );
	} else {
		return array();
	}
}

/**
* Remove emoji CDN hostname from DNS prefetching hints.
*
* @param  array  $urls          URLs to print for resource hints.
* @param  string $relation_type The relation type the URLs are printed for.
* @return array                 Difference betwen the two arrays.
*/
function disable_emojis_remove_dns_prefetch( $urls, $relation_type ) {
	if ( 'dns-prefetch' == $relation_type ) {
		// Strip out any URLs referencing the WordPress.org emoji location
		$emoji_svg_url_bit = 'https://s.w.org/images/core/emoji/';
		foreach ( $urls as $key => $url ) {
			if ( strpos( $url, $emoji_svg_url_bit ) !== false ) {
				unset( $urls[$key] );
			}
		}
	}
	return $urls;
}