gtm wordpress

/**
 * Google tagmanager
 */
add_action( 'wp_head', 'head_scripts' );
function head_scripts() { ?>
	<!-- 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=
			'//www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
		})(window,document,'script','dataLayer','GTM-XXXXX');</script>
	<!-- End Google Tag Manager -->
	<?php
}
add_action( 'wp_footer', 'body_scripts' );
function body_scripts() { ?>
	<!-- Google Tag Manager -->
	<noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-XXXXX"
	                  height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
	<!-- End Google Tag Manager -->
	<?php
}

The body script should be place as early as possible too. The best implementation I have seen so far just uses a custom hook placed immediately after opening the body tag. Example https://stackoverflow.com/a/31226533/1214176