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:

<?php

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

Instructions

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:

<?php

isNeutralSoldier('yellow', 'black'); // true
isNeutralSoldier('red', 'black');    // false
isNeutralSoldier('red', 'red');      // false