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PHP: Logical Operators 2

Logical operators are an important topic, so it's worth reinforcing them with some more examples and practice.

Let's try to implement a function that checks a year to see if it's a leap year. A year is a leap year if it's a multiple of 400, or if it's both a multiple of 4 and not a multiple of 100. As you can see, the definition already contains all the required logic, all we need to do is to put it into code:


function isLeapYear($year)
    return $year % 400 === 0 || ($year % 4 === 0 && $year % 100 !== 0);

isLeapYear(2018); // false
isLeapYear(2017); // false
isLeapYear(2016); // true

Let's break it down piece by piece:

  • the first condition, $year % 400 === 0: means the remainder of division by 400 is 0, so the number is a multiple of 400
  • || OR
  • second condition ($year % 4 === 0 && $year % 100 !== 0)
    • year % 4 === 0: means the remainder of division by 4 is 0, so the number is a multiple of 4
    • && AND
    • $year % 100 !== 0: means the remainder of division by 100 is not 0, so the number is not a multiple of 100


Write a function isNeutralSoldier(), that takes two arguments as input:

  1. Armor color (string). Possible variants: red, yellow, black.
  2. Shield color (string). Possible variants: red, yellow, black.

The function returns true if the color of the armor is not red and the color of the shield is black. In other cases, it returns false.

Call examples:


isNeutralSoldier('yellow', 'black'); // true
isNeutralSoldier('red', 'black');    // false
isNeutralSoldier('red', 'red');      // false
The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

  • Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

I've read the lessons but nothing is clear 🙄

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