Working with PHP Functionality Inside of Wordpress

Hi all, I have moderate level PHP programming skills. I am also interested in merging those skills inside of the WordPress app. With their advanced responsive design themes and many other functions it seems like a good idea. I have tried loading some PHP plug-ins in WP – but I don't seem to get them to do more than basics. For example, I am looking to be able to perform moderate level PHP/MySQL functionality such as C.R.U.D. / perform basic queries to the database and display the results with various looping functions etc. all the basics we would be doing on an average PHP driven website. In other words build a php/mysql website but simple inside of WP. Currently, I don't know how it's possible to do this inside of posts and pages. Of course somehow this is possible, since there are plug-ins like woo commerce where they have built a whole php driven store functionality in a plug-in. Q: So, I'm curious if anybody knows how I can get started working with PHP/MySQL inside of the WordPress app? -- Thanks, Dave - DealTek dealtek@gmail.com [db-14]