Google Tag Manager

function add_gtm_script() {
    ?>
    <!-- Google Tag Manager -->
    <script>
    (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});
    var f=d.getElementsByTagName(s)[0], j=d.createElement(s), dl=l!='dataLayer'?'&l='+l:'';
    j.async=true; j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;
    f.parentNode.insertBefore(j,f);
    })(window,document,'script','dataLayer','GTM-WXR2BQ93');
    </script>
    <!-- End Google Tag Manager -->
    <?php
}
add_action('wp_head', 'add_gtm_script');
function add_gtm_noscript() {
    ?>
    <!-- Google Tag Manager (noscript) -->
    <noscript>
        <iframe src="https://www.googletagmanager.com/ns.html?id=GTM-WXR2BQ93"
        height="0" width="0" style="display:none;visibility:hidden"></iframe>
    </noscript>
    <!-- End Google Tag Manager (noscript) -->
    <?php
}
add_action('wp_body_open', 'add_gtm_noscript');