Hi, I know html and css. I also know some php/mysql. But how do you start to create a webapplication. I want to create an online marketplace but how do you plan it etc? Can someone give me the right direction etc? Thanks
Web applications a umbrella term, you could call anything you'd write in PHP a "Web Application", there is no definite definition for it, but you should look on wikipedia, its a huge rabbit hole once you start reading through there. Online Marketplaces are quite tricky, they involve interaction of multiple technologies to actually be of any use, and integrated with checkout engines like paypal, google checkout, theres alot of tedious work involved in writing one and theres a lot of competition here from serious companies that have very serious products, theres also alot of very advance open source/free solutions, so if your looking to build something thats commercial, thats my 2c. Otherwise, if its learning, if you have a good grasp of PHP and MYSQL, you should know about where to start, if not, i suggest reading documentation of existing CMS's(content management systems) to see how they work, you can gain some insight that way into what will it require to design and deploy such a system.
The easiest way is using open source. Develope a large system cost a lot of time and you need experience too