Adding Favicon and Apple Touch icon in WordPress using theme and plugin

apple-touch-icon.php

<?php
function add_apple_touch_icon</span>(){
    echo '<link rel="apple-touch-icon" href="'. get_template_directory_uri() .'images/apple-touch-icon.png">';
}

add_action('wp_head','add_apple_touch_icon');

favicon-plugin.php

<?php
/**
 * Plugin Name: My Favicon
 * Description: Activating a favicon into my site.
 */

function add_my_favicon() {
    $favicon_path = plugins_url( '/favicon.ico', __FILE__ );

    echo '<link rel="shortcut icon" href="'. $favicon_path .'" />';
}

add_action( 'wp_head', 'add_my_favicon' ); //front end
add_action( 'admin_head', 'add_my_favicon' ); //admin end

functions.php

<?php
function add_my_favicon() {
   $favicon_path = get_template_directory_uri() . '/images/favicon.ico';

   echo '<link rel="shortcut icon" href="'. $favicon_path .'" />';
}

add_action( 'wp_head', 'add_my_favicon' ); //front end
add_action( 'admin_head', 'add_my_favicon' ); //admin end