PHP: Magic numbers

Let's remember one of the previous lessons:

<?php

$eurosCount = 1000;
$dollarsCount = $eurosCount * 1.25; // 1250
$rublesCount = $dollarsCount * 60;  // 75000

print_r($rublesCount);

From the developer's point of view, such code "smells". This describes code that doesn't conform to so-called best practices. And here's the reason. If you're looking at the numbers 60 and 1.25, you'll probably be wondering, "What are those numbers? Imagine reading a month from now! How could a new programmer who hasn't seen the code before understand it? In our example, the context is restored through proper naming, but real life code is much more complicated, and therefore it's often impossible to guess the meaning of the numbers.

This "smell" is caused by magic numbers. They're numbers that you can't explain the origin of, unless you dig deeper into the code.

The way out is simple: just create variables with the right names and everything will be as they need to be.

<?php

$dollarsPerEuro = 1.25;
$rublesPerDollar = 60;

$eurosCount = 1000;
$dollarsCount = $eurosCount * $dollarsPerEuro;   // 1250
$rublesCount = $dollarsCount * $rublesPerDollar; // 75000

print_r($rublesCount);

Note the following details:

• lowerCamelCase naming
• The two new variables are separated from the following computations by an empty string. These variables are meaningful even without any computation involved, which is why separating them here is good, it makes it easier to read.
• The code is well named and structured, but it's longer than the previous version. This is often the case, but it's fine, because the code needs to be readable.

Instructions

You've come across this code, which prints the total number of rooms owned by the present king:

<?php

$king = 'King Balon the 6th';
print_r($king . ' has ' . (6 * 17) . ' rooms.');

As you can see, there are some magic numbers here: it's unclear what 6 is and what 17 is. If you know the history of the royal family, you can guess: each new king inherits all his ancestors' castles and builds a new one, an exact copy of his parents'.

This strange dynasty simply breeds identical castles…

Get rid of the magic numbers by creating new variables and then displaying the text on the screen.

You'll get this:

King Balon the 6th has 102 rooms.

Variable names should convey the meaning of numbers, but should remain short and succinct enough to be easily read.

Note: The code will work with any name, and we only check the printed result, so the task is up to you.