PHP: Magic constants
In addition to the usual constants, PHP has a separate group of magic constants. The differences are as follows:
- You can't define magic constants yourself, you can only use existing ones.
- Magic constants begin and end with
- The magic is that the constants have the same value only within a certain part of the program.
This last point may seem strange. What kind of constants are they if their value changes? To put it bluntly, they're not very constant, but their changes are clearly regulated and in practice don't cause problems. Such constants include, for example, the following:
__LINE__— contains the current line of the file it's used in
__FILE__— path to the current file
__DIR__— the path to the directory where the current file is located
Output the path to the current directory using a magic constant.
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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A magic constant is a special constant available in PHP; it contains different values in different contexts.