PHP lesson 4: Arithmetic: / % ** and intdiv()

For parents: how to use this lesson

You don't need to know PHP yourself. The lesson explains each step on screen, the way Mr Babbage, our Head of Computing, likes it: a worked example first, then a go for your child. Your child predicts what code prints, traces it and puts it in order – marked straight away – and then writes and fixes real PHP in the practice test, where it runs in the browser.

1. Read what your child will learn together.
2. Press Start the lesson below. Sit with your child for the teaching and the worked example (about 16 minutes): ask them to say what each line does.
3. Let them do the practice on their own, then the write-it and fix-it questions in the practice test. When code goes wrong, PHP's message is a clue – let them read it out and try again before you help.
4. Finish with the talk question: How could you use % to test whether a number is even?

Watch out for

• 7 / 2 is 3. In PHP / gives 3.5 – use intdiv() for 3.
• % means percent. % gives the remainder after dividing.

Miss Lovelace's tip for home: ask your child to explain one line of their program to you in their own words. If they can explain it, they understand it – and every message from PHP is a clue, not a failure.