Modify a Wordpress site

I am looking for someone to assist in incorporating a search engine into a Wordpress site and have the results displayed in a template page so that it ties in with the look of the rest of the site.

The search engine coding has been produced and works fine although the problem I am facing is the layout of the results page. I have tried to add the coding myself so that the results are displayed in a template page similar to the pages already in place on the Wordpress site, but when I go to use the search engine it produces the following error:

Fatal error: Call to undefined function get_header() in /home/hattscou/public_html/wp-content/themes/custom/headtohead.php on line 12

When I remove the from my coding the results page loads.

I therefore need someone to hopefully create the results page so that it is set up like the rest of the site and displays the Wordpress template files (header and footer) as well as the search results in the content section.

If possible the page address would also be displayed as siteurl.co.uk/ headtohead.php instead of the long format of siteurl /wp-content/themes/custom/headtohead.php which is currently shown