PHP: Explicit type conversion
Type conversion is a fairly common operation in web development. On the one hand, you can rely on weak typing to perform it, on the other hand, in many situations it's better to do the conversion explicitly, using special syntax. This code is clearer and more predictable.
<?php
// These examples are a bit artificial. In reality, this mechanism is much more useful when using variables
print_r((string) 5);
print_r((int) '345');
Explicit type conversion works like this: the desired type is specified before the value, in parentheses. As a result, the value on the right is converted to a value of the other type specified on the left in brackets. We're currently only familiar with two types, but the conversion works for any type. For example, when converting a fractional number to a whole number, the number will be rounded down
<?php
print_r((int) 5.73); // => 5
Type conversion can be used within compound expressions:
<?php
// Additional brackets help to visually separate parts of an expression from each other
print_r('This is ' . ((string) 5));
Это 5
In more complex situations (when using functions that are passed later) multiple conversions are encountered: (string) (5 + ((int) '4')). The procedure for calculating this expression is as follows:
<?php
(int) '4'; // 4
5 + 4; // 9
(string) 9; // '9'
Instructions
Output the string 2 times from the number 2.9 and the string times using type conversion and concatenation. This requires two conversions: first, to an integer and then to a string
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\TypeConversion;
4
5use PHPUnit\Framework\TestCase;
6
7\HexletBasics\Functions\runScript();
8
9class Test extends TestCase
10{
11 public function test()
12 {
13 $expected = '2 times';
14 $this->expectOutputString($expected);
15 require 'index.php';
16 }
17}
18Teacher's solution will be available in:
