PHP: Elvis operator
Imagine the following problem: users can have names and pseudonyms on a given website. The name isn't necessary, but a user has one, this person should be addressed by their first name, and if not, you should address them by their pseudonym.
Let's try to assemble a string that greets users according to these requirements:
<?php
function generateGreeting($name, $nickname)
{
if ($name) {
return "Hello, {$name}!";
} else {
return "Hello, {$nickname}!";
}
}
generateGreeting('Bob', 'CoolBob86'); // 'Hello, Bob!'
generateGreeting('', 'CoolBob86'); // 'Hello, CoolBob86!'
We've taken advantage of the fact that PHP converts types. In the if ($name) code, PHP will turn $name into a bool type; if it's an empty string, it will return false, otherwise, it'll return true.
You can use a ternary operator to write it in an even shorter way:
<?php
function generateGreeting($name, $nickname)
{
return $name ? "Hello, {$name}!" : "Hello, {$nickname}!";
}
This is a common situation: we work with bool values and get the first value if it's true and the second if it isn't.
In PHP, there's a special operator for such cases:
<?php
function generateGreeting($name, $nickname)
{
$user = $name ?: $nickname;
return "Hello, {$user}!";
}
?: is a binary operator that returns the first operand if it's true, and the second if it isn't.
It's called Elvis because:
Also, Elvis sounds a bit like "else if".
Instructions
Write a function, generateAmount(), that takes two numbers: the number of items and the cost of an audit. If there are 0 goods, the function returns the cost of the audit multiplied by 3. If there aren't 0 goods, the function returns the number of goods.
Call examples:
<?php
generateAmount(0, 2); // 6
generateAmount(0, 5); // 15
generateAmount(1, 2); // 1
generateAmount(12, 49); // 12
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 🙄
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.
Tips
Definitions
The Elvis operator is an expression that returns the first operand if it's true, and the second if it isn't. For example,
$name ?: $nickname;.