PHP: Data types
There are different ways to represent data in programs.
There are strings — sets of characters in quote marks, like "Hello, World!". There are integers — for example, 7, -198, 0. These are two different categories of information — two different types of data.
The multiplication operation makes sense for integers, but it makes no sense for strings; why would you want to multiply the word "mom" by the word "notepad"?
The data type defines what can be done with the elements from a particular set of elements
PHP recognizes types. Therefore, it won't allow us to multiply a string by a string ("text by text"). But it will allow you to multiply an integer by another integer. The existence of types and these restrictions in the language protects programs from accidental errors.
Unlike strings, numbers don't need to be wrapped in quotes. To print the number 5, all you have to do is write:
<?php
print_r(5);
Note that the number 5 and the string '5' are completely different things, although print_rs output for this data is identical.
Integers (1, 34, -19 etc.) and rational numbers (1.3, 1.0, -14.324 etc.) are two separate data types. This division is due to the peculiarities of how computers are set up. There are other types, which we'll get to know later.
Here's another example, but with a rational number:
<?php
print_r(10.234);
The data types "string", "integer" and "rational number" are primitive types and are built into the PHP language itself. Some composite data types are also built into the language, but for now we'll only work with the primitive ones. Programmers can also create their own data types.
For example, in the code above, there are three lines and no strings.
Instructions
Print the number -0.304.
Tips
Definitions
- A data type
- Primitive data types are simple types built into the programming language itself.
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\DataTypes\PrimitiveDataTypes;
4
5use PHPUnit\Framework\TestCase;
6
7\HexletBasics\Functions\runScript();
8
9class Test extends TestCase
10{
11 public function test()
12 {
13 $expected = '-0.304';
14 $this->expectOutputString($expected);
15 require 'index.php';
16 }
17}
18Teacher's solution will be available in:
