Make Google Analytics listen to Browser "Do Not Track" in WordPress

mu-plugin-do-not-track.php

<?php
	add_filter('opt_out_settings', function($settings) {
		// this will work in most sites with a plugin to use Google Analytics.
    $settings['id'] = autodetect_google_analytics_code(); 

    // OR!
    
    // use this line to be sure;
    $settings['id'] = 'UA-1234567-89'; // <-- your analytics property code here
    
    // OPTIONAL: use a cookie to disable Analytics
    $settings['cookie_name'] = false; // set a cookie name here defined by your custom cookie-bar
		$settings['cookie_value'] = false; // set the value to look for when analytics should be OFF.

		return $settings;
	});

  add_action('wp_head', function(){
		$id = $cookie_name = $cookie_value = '';
		extract(apply_filters('opt_out_settings', compact('id', 'cookie_name', 'cookie_value')));
		if ($id) { 
		?><script id="ga-opt-out">
			(function(_d, _w) { 
				var dnt = false;
				if ('msDoNotTrack' in navigator) dnt = (navigator.msDoNotTrack === 'on' || navigator.msDoNotTrack === 'yes' || navigator.msDoNotTrack === "1" || navigator.msDoNotTrack === 1);
				if ('doNotTrack' in navigator) dnt = (navigator.doNotTrack === 'on' || navigator.doNotTrack === 'yes' || navigator.doNotTrack === "1" || navigator.doNotTrack === 1);
				if ('doNotTrack' in window) dnt = (window.doNotTrack === 'on' || window.doNotTrack === 'yes' || window.doNotTrack === "1" || window.doNotTrack === 1);
<?php if ($cookie_value && $cookie_name) { ?>
				dnt = dnt || _d.cookie.match(/(^|[; ])<?php print preg_quote($cookie_name); ?>=<?php print preg_quote($cookie_value); ?>(;|$)/);<?php } 
?>				_w['ga-disable-<?php print esc_attr($id); ?>'] = dnt; 
			})(document, window);
		</script><?php
		}
	}, ~PHP_INT_MAX);

	function autodetect_google_analytics_code() {
		global $wpdb;
		$uas = $wpdb->get_col("SELECT option_value FROM {$wpdb->options} WHERE option_value LIKE '%UA-%'");
		$uas = array_map(function($el) { return preg_match('/(UA-[0-9]+-[0-9]+)/', $el, $m) ? $m[1] : false; }, $uas);
		$uas = array_unique($uas);
		$uas = array_filter($uas);
		$uas = array_values($uas);
		if (count($uas) === 1) {
			return $uas[0];
		}
    return false;
	}