Need some help with PHP & mySQL

Digital marketing is broad but can be plainly described as: the creation, distribution of and engagement with, relationship or brand building content in an electronic format.

I would probably look at a course on udemy for that specific case https://www.udemy.com/getting-started-with-php-programming/?dtcode=MzjhAx31ASRH

Zend Framework 2 is one of the most used Frameworks out there standing next to Symfony 2/3. For example the Magento Shop Engine is based on Zend Framework 1 as well. This said Zend Framework 2 is a good choice for web applications in general and there are lot's of developers out there. Zend.com even offers certifications as Zend Framework 2 Certified Architect - so you can use their Yellowpages to find capable developers. Anyways I would not recommend to start creating an ecommerce site from scratch since the existing engines provide so much more than a nice frontend for customers and payment gateway integrations. There are many existing engines you can customize - what most shops do.

Be careful when simply wrapping things into a mobile app. This can backfire on you and you could be presented with some very harsh edge cases. PHP isn't going to be encapsulated so much as the HTML/CSS/JavaScript. So keep in mind your mobile application could likely be in a position of requiring an online connection to work (because it must interface with your existing hosted WordPress site). This could also mean your hosting solution needs to be evaluated to ensure you can handle any increased traffic (and those traffic patterns could be different when coming from a mobile app that perhaps loads things the user doesn't see right away, accesses content that may not be cached, etc.). You want to ensure your server doesn't go down because then your mobile app would be "down" as well. That said... Things like Phonegap (web views) are a wonderful idea for utility apps because the performance is good enough for those (and hey even some games) and they end up being easily ported across many mobile operating systems. I would look into Phonegap, Appgyver (a new and totally awesome one because parts of it will utilize the native OS and your app will feel more responsive), Appcelerator Titanium, and perhaps even the new Famo.us one. Also take a look at the Ionic Framework for some further ideas about mobile UI and what you can do with these web view style apps.

I think you're not fully embracing the lean startup methodology. Is your SaaS handling some operations that are a matter of life and death or critical mission thing for an organization? if the answer is No start with simplest option and do a soft launch and invite some carefully selected (50) beta testers. Get the service going and gather feedback as much as possible. Then when you're at version 1.5 or 2.0 you'd know the problem you're solving a lot better. Slavi, Orbisius & qSandbox