Example of custom Google Analytics integration for SilverStripe CMS

config.yml

---
Name: mysite
After:
  - 'framework/*'
  - 'cms/*'
---
# YAML configuration for SilverStripe
# See http://doc.silverstripe.org/framework/en/topics/configuration
# Caution: Indentation through two spaces, not tabs
SSViewer:
  theme: 'simple'
SiteConfig:
  extensions:
    - GoogleAnalyticsExtension

google-analytics.js

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
        (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
    m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

ga('create', '$trackingid', 'auto');
ga('send', 'pageview');

//Event tracking or any other advanced GA code
$('a#important-download').click(function() {
    ga('send', 'event', 'important-ebook', 'download', 'Marketing Campaign');
});

GoogleAnalyticsExtension.php

<?php
class GoogleAnalyticsExtension extends DataExtension {

    private static $db = array(
        'GoogleAnalyticsTrackingID' => 'Varchar(11)',
    );

    public function updateCMSFields(FieldList $fields)
    {
        $fields->addFieldToTab('Root.GoogleAnalytics', TextField::create('GoogleAnalyticsTrackingID')->setDescription('e.g. UA-XXXXX-XX'));
    }
}

Page.php

<?php
class Page extends SiteTree {

}
class Page_Controller extends ContentController {

	public function init() {
		parent::init();

		Requirements::javascriptTemplate(
			'mysite/javascript/google-analytics.js',
			array(
				'trackingid' => SiteConfig::current_site_config()->GoogleAnalyticsTrackingID,
			)
		);
	}

}