I teach an introductory web development class (html and css) and last week one of my students wanted to see some PHP, if you do not know what PHP is, it is a programming language used to build dynamic websites. Anyway his eyes kind of glossed over when I showed him and started taking about it… Back end programming is not something someone can just ‘pick up’ quickly, it takes a lot of learning to understand and be able to write it. Part of the value in hiring a qualified developer is their knowledge of server side programming languages like PHP (among many others), this knowledge means your developer can handle any situation that arises.
I ran across an individual that claimed to be a web developer, so I checked out his website and saw he only develops using WordPress, and the majority of his services are out of the box type of services, nothing custom coded. WordPress is a great platform for development, it can speed up developing time and allow the client to update information themselves, but if a developer can ONLY develop in WordPress, I would say that is a red flag. What if you need something above and beyond the scope of any WordPress Plugin? What if a problem arises that requires custom code or database fixes? I realize it is hard for most people to understand what makes someone qualified to be a developer, it would be like asking me what makes someone qualified to be a Railroad Conductor (I have no clue) So if I had to choose one thing for you to use when deciding if someone is qualified to be a developer, I would say make sure your developer can custom code, using Object Oriented Programming.