"Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites. You can configure your engine to search both web pages and images. You can fine-tune the ranking, add your own promotions and customize the look and feel of the search results. You can monetize the search by connecting your engine to your Google AdSense account."
This script enables you to use Google API facilities using PHP to your own web site styled to your own way. This script has Standard Search Element and Also Custom Search JSON API. Standard Search Element is FREE from Google and JSON API is not free but we have 100 queries free per day. Please read the following to read more on Google CSE