PHP Caching Code on Existing PHP Site

I have an existing custom site done in PHP. It's a directory type site that pulls data from a MySQL database dynamically depending on search input from the user. It's a simple site that is seeing an increase in traffic and is causing some issues with my server. I need to install some caching code that will help with the traffic. However, I'm not sure what code to add. My host company added some code to the htaccess file but other than that there is no caching. The site is not that large, only a handful of pages so I will need a coder that can help me identify what needs to be done and will send me the code I need to optimize the pages. I will edit the pages accordingly and upload to my server. This should be an easy project for the right coder.