I had to create a PHP program using the getdate() function (don't search if you don't know about). Suffice to say that I wanted to do something that really requires this function (returning an array) and not a simpler one (as date()).
I chose to create a chronometer but soon realized that using two forms (one to start, one to stop), my first value was lost whatever I did... I understood that I had to store the data in an external place but I'm not supposed to use database right now, damned. And bingo! I remembered reading how to write into a text file or read from it. Now it's working. I'm the best, yup!
Old and clever programmers, don't laugh at me; you met the same kind of problems when you began... Just remember how high you felt when finding the solution LOL