How to automatically select a category by the title of the text?

Question

PHP

Hello, I saw on one site, when adding an ad for the sale of spare parts, entering the title of the product, its category is automatically selected, how is this implemented? When you enter one word, then I understand that you are looking for matches and display a category, but when there are several words in the title?
Is there some kind of dictionary, according to which each word from the title is run and the category is found by coincidence? So what?

Answer 1

machine learning
there are a number of ways - from bag words / k-means to all sorts of Bayes