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PHP: Concatenation

We are already familiar with the mathematical operation of addition. This program:


print_r(5 + 3);

will print '8' to the screen, which is the result of operation of binary operator '+' with operands '5' and '3'.

Strings can be manipulated too. You can "add" two strings. This program:


print_r('Dragon' . 'stone');

will output Dragonstone to the screen - the result of operation of binary operator '+' with operands 'Dragon' and 'stone'.

Such operation is called concatenation. Roughly speaking, it's 'glueing' strings together. Such glueing always happens in the same order as the operands follow each other, in other words, the left operands becomes the left part of the string, and the right operand - the right part.

Here are some more examples:


print_r('Kings' . 'wood');     // => Kingswood

print_r('Kings' . 'road');     // => Kingsroad

print_r("King's" . 'Landing'); // => King'sLanding

As you see from examples above, strings can be concatenated even if they are specified with different quotation marks.

In the last example we got the name of the city printed incorrectly: King's Landing must have a space between words! The original strings, however, didn't have spaces, and the spaces to the right and left of . are not interpreted as part of strings.

We can fix this in several ways:


//Adding a space at the end of the left part
print_r("King's " . 'Landing'); // => King's Landing

//Adding a space at the end of the right part
print_r("King's" . ' Landing'); // => King's Landing

The more spaces we add, the wider interval we get:


print_r("King's " . ' Landing');   // => King's  Landing

print_r("King's  " . '  Landing'); // => King's    Landing


Print to the screen

Winter came for the House of Frey.

using word concatenation.

The exercise doesn't pass checking. What to do? 😶

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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 🙄

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  • Concatenation - operation of joining two strings. For example, print_r("King's " . ' Landing');`

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