PHP: Extracting characters from string
Sometimes, you need to get a single character from a string. For example, if a website knows the user's first name and surname, and at some point, it needs to output it asJ. Smith, you need to take the initial letter from the first name.
<?php
$firstName = 'Alexander';
print_r($firstName[0]); // => A
Square brackets with a number are a special string extraction operator. This number is called an index — the position of the character inside the string. Indexes start with 0 in almost all programming languages, so to get the first character, you must specify index 0. The index of the last element is equal to the length of the string minus one:
<?php
$firstName = 'Alexander';
// The length of the string is 9, so the last index is 8
print_r($firstName[8]); // => r
// Self-check. What will this code print?
$magic = '\nyou';
print_r($magic[1]); // => ?
You're allowed to use negative indices. In this case there's a reference to characters starting from the end of the string. -1 is the index of the last character, -2 of the penultimate, and so on. Unlike direct indexing, reverse indexing counts down from -1:
<?php
$firstName = 'Alexander';
print_r($firstName[-1]); // => r
You can use variables as well as numbers as an index. Here's an example that will have the same result of displaying the character A, but the index inside the square brackets is written as a variable instead of a number:
<?php
$firstName = 'Alexander';
$index = 0;
print_r($firstName[$index]); // => A
Instructions
You've been given three variables with the names of different people. Put together and print a word out from the characters in this order:
- The third character from the first line.
- The second character from the second line.
- The fourth character from the third line.
- The fifth character from the second line.
- The third character from the second line.
Try using interpolation: you can put individual characters (called via square brackets), as well as variables, inside curly brackets.
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.
Your exercise will be checked with these tests:
1<?php // phpcs:ignore PSR1.Files.SideEffects
2
3namespace HexletBasics\Variables\Symbols;
4
5use PHPUnit\Framework\TestCase;
6
7\HexletBasics\Functions\runScript();
8
9class Test extends TestCase
10{
11 public function test()
12 {
13 $expected = 'hodor';
14 $this->expectOutputString($expected);
15 require 'index.php';
16 }
17}
18Teacher's solution will be available in:
