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PHP: Interpolation

In the lesson on concatenation, we had the task of creating a letter header out of two variables and punctuation marks. You most likely did it this way:


$firstName = 'Joffrey';
$greeting = 'Hello';

print_r($greeting . ", " . $firstName . "!");

It's a pretty simple case, but, and you'll probably agree, it looks a little unseemly. You have to watch out for several quotation marks and spaces, and you can't tell where something starts and ends without paying attention.

There is a more convenient and elegant way to solve the same problem: interpolation. This is what it looks like:

$firstName = 'Joffrey';
$greeting = 'Hello';

print_r("{$greeting}, {$firstName}!"); // => Hello, Joffrey!

We just created one line and inserted variables into it in the right places using curly brackets ({}). It's like we have a blank form where we can enter the desired values. And we no longer have to worry about separate strings for punctuation marks and spaces, all of these characters already exist in our template string.

You can make as many bracketed blocks as you want on one line.

Interpolation only works with double-quoted strings.

Nearly all languages favor interpolation over concatenation for combining strings. It glues a string together, and spaces and other characters look good in it.


Display the line Do you want to eat, ?. And the variable$starkshould be used instead of`. The output should look like this:

Do you want to eat, Arya?
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.

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  • Interpolation is a way to join strings by inserting variable values into a string template using curly brackets. For example, \"Hi, {$name}!\".

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