In web development, programs use strings all the time. Everything we see on websites, in one way or another, is presented as text. This text is most often dynamic, it's made up of different connected pieces. The operation of joining strings in programming is called concatenation.
We already know about addition in mathematics. This sort of program:
<?php print_r(5 + 3);
8 — the result of the binary operator
+ with operands
You can add two strings. This sort of program:
<?php print_r('Dragon' . 'stone');
Dragonstone — the result of the binary operator
. with the operands 'Dragon' and 'stone'.
Strings are always concatenated in the order in which the operands are written. The left operand becomes the left part of the string, and the right one becomes the right part.
Here are a few more examples:
<?php print_r('Kings' . 'wood'); // => Kingswood print_r('Kings' . 'road'); // => Kingsroad print_r("King's" . 'Landing'); // => King'sLanding
As you can see, strings can be concatenated even if they're written in different quotes.
In the last example, the name of the city has been misspelled: King's Landing should be spelled with a space! But there were no spaces in our initial lines, and the spaces in the code itself to the left and right of the
. character don't matter, because they're not part of the strings.
There are two ways to fix this:
<?php // Put space at the end of the left part print_r("King's " . 'Landing'); // => King's Landing // Put a space at the start of the right part print_r("King's" . ' Landing'); // => King's Landing
Space is a character like any other, so however many spaces you put in the string is how many you'll get:
<?php print_r("King's " . ' Landing'); // => King's Landing print_r("King's " . ' Landing'); // => King's Landing
Winter came for the House of Frey.
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.
Concatenation is the operation of joining two strings. For example,
print_r("King's " . ' Landing');