google-tag-for-wp.php

<?php
/**
 * Add Google tag to WordPress.
 *
 * @wordpress-plugin
 * Plugin Name: google-tag-for-wp.
 * Description: Add the Google tag to the header of a WordPress site.
 * Plugin URI: n/a
 * Version:     1.0.0
 * Author:      Adam Silverstein, Google
 * License:     Apache License 2.0
 * License URI: https://www.apache.org/licenses/LICENSE-2.0
 */

$ga_tag = "{$ga_tag_dynamic_value}";

/**
 * This function will add the ga tag to the WordPress header.
 */
function ga_atfwp_add_google_analytics_tag( $ga_tag ) {
?>

<!-- Google tag (gtag.js) -->
<script async src="https://www.googletagmanager.com/gtag/js?id=TAG_ID"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());

gtag('config', '<?php echo esc_attr( $ga_tag ); ?>');
</script>
<?php
}
add_action( 'wp_head', 'ga_atfwp_add_google_analytics_tag' );