Many languages include a switch in addition to the conditional if construct. This is a specialized version of if, designed for certain cases. For example, it makes sense for us to have an if else chain for equality checks. For example:
<?php
if ($status === 'processing') {
// Doing it once
} elseif ($status === 'paid') {
// Doing it twice
} elseif ($status === 'new') {
// Doing it three times
} else {
// Doing it four times
}
This composite check has one distinguishing feature, each branch here is a check for the value of the status
variable. Switch allows you to write this code in a shorter and more expressive way:
<?php
switch ($status) {
case 'processing': // status == processing
// Doing it once
break;
case 'paid': // status == paid
// Doing it twice
break;
case 'new': // status == new
// Doing it three times
break;
default: // else
// Doing it four times
}
A switch is a rather complicated construction in terms of the number of elements it consists of:
switch
. A variable whose values switch use to select a behavior. And curly brackets for behavior branches.case
and default
constructions, where the behavior for different values of the variable is described. Each case corresponds to an if
in the example above. default
is a special situation, corresponding to the else
branch in conditional constructions. Like with else
, there's no need to specify default
.break
is needed to prevent it from not working properly. If it's not specified, then after the desired case
is executed, the execution will go to the next case
and so on either until it reaches the nearest break
, or until the end of the switch.The curly brackets in the switch don't define a block of code like they did elsewhere. Only the syntax shown above is acceptable. In other words, you can use case
or default
there. But inside each case
(and default
) the situation is different. You can execute any code you like here:
<?php
switch ($count) {
case 1:
// Doing something useful
break;
case 2:
// Doing something useful
break;
default:
// Doing something
}
Sometimes, the result inside case
means ending the function containing the switch. If this happens, you need to return it outside somehow. There are two ways to do this.
The first way. Create a variable before switch, fill it with something in case and then return the value of that variable outward at the end.
<?php
function doSomethingGood($count)
{
// Filling it
switch ($count) {
case 1:
$result = 'one';
break;
case 2:
$result = 'two';
break;
default:
$result = null;
}
// Return
return $result;
}
The second way is easier and shorter. Instead of creating a variable, case allows you to internally do a normal return from a function. And since no code is executed after return
we can get rid of break
:
<?php
function doSomethingGood($count)
{
switch ($count) {
case 1:
return 'one';
case 2:
return 'two';
default:
return null;
}
}
Though switch is present in the code, you can always find a way to avoid it. The key benefit of using it is that it better expresses the programmer's intention when checking the values of a particular variable. Although there's now physically more code, it's easier to read than loads of elseif blocks.
Write a function, getNumberExplanation()
, that describes a number passed to it. If there's no explanation available, it returns null
:
<?php
getNumberExplanation(8); // null
// There are explanations only for the following numbers
getNumberExplanation(666); // 'devil number'
getNumberExplanation(42); // 'answer for everything'
getNumberExplanation(7); // 'prime number'
If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:
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.
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.
It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.
By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.
Your exercise will be checked with these tests:
1<?php
2
3namespace HexletBasics\Conditionals\SwitchStatement;
4
5use PHPUnit\Framework\TestCase;
6
7class Test extends TestCase
8{
9 public function test()
10 {
11 require 'index.php';
12
13 assert(getNumberExplanation(0) === 'just a number');
14 assert(getNumberExplanation(666) === 'devil number');
15 assert(getNumberExplanation(42) === 'answer for everything');
16 assert(getNumberExplanation(7) === 'prime number');
17 }
18}
19
Teacher's solution will be available in: