Add Google Analytics to WordPress head (header.php)

functions.php

<?php

/**
 * Add Google Analytics
 * Add this to your theme functions.php file
 * @link https://gist.github.com/samkent/1df2429b6505c272c7a6bf5799844840
 */
add_action('wp_head', 'google_analytics');
function google_analytics() {
	?>
		<!-- Paste your Google Analytics JS Tracking Code here -->
	<?php
}