Ask HN: Input keyword to calculation

Hello all, I'm new to HN. So its christmas break, and I'm working on some side projects. One project I'm working on is to take some entered text from an input and do some calculations (ie "I bought 5 grand theft auto games"). Then when the user submits this query they might be returned the total aggregate price. Any ideas how to program this? I started by laboriously creating a database table with subject, verb, object and quantity and then some PHP to calculate stuff, but am wondering if there is a more clever way.

Also, somewhat unrelated, but I'm currently studying machine learning techniques for my PhD, and I'm really curious how to implement it for web applications. Any thoughts or resources? Take care