PHP: Data Aggregation (Strings)
You can use aggregation with strings as well as with numbers. In most cases, this applies to dynamic string generation, where you don't know in advance what size the string will be and what it will contain.
Imagine a function that multiplies a string, i.e., it repeats a string a given number of times:
<?php
repeat('hexlet', 3); // 'hexlethexlethexlet'
The core mechanism of this function is simple, the loop increments through the string a given number of times:
<?php
function repeat($text, $times)
{
// For strings, the neutral element is an empty string
$result = '';
$i = 1;
while ($i <= $times) {
// Add a string on each iteration
$result = "{$result}{$text}";
$i = $i + 1;
}
return $result;
}
Let's break down down the code's execution into steps:
<?php
// To call repeat('hexlet', 3);
$result = '';
$result = "{$result}hexlet"; // hexlet
$result = "{$result}hexlet"; // hexlethexlet
$result = "{$result}hexlet"; // hexlethexlethexlet
Instructions
Write a function, joinNumbersFromRange(), which joins all numbers in a range into a string:
<?php
joinNumbersFromRange(1, 1); // '1'
joinNumbersFromRange(2, 3); // '23'
joinNumbersFromRange(5, 10); // '5678910'
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.
languages.lessons.show.chat.guest
Your exercise will be checked with these tests:
1<?php
2
3namespace HexletBasics\Loops\AgregationString;
4
5use PHPUnit\Framework\TestCase;
6
7class SolutionTest extends TestCase
8{
9 public function test()
10 {
11 require 'index.php';
12
13 $this->assertEquals('2', joinNumbersFromRange(2, 2));
14 $this->assertEquals('12345', joinNumbersFromRange(1, 5));
15 $this->assertEquals('101112', joinNumbersFromRange(10, 12));
16 }
17}
18Teacher's solution will be available in:
