PHP: What is a variable
Imagine we need to type the phrase Father! twice or even five times on the screen. You can solve it via brute force:
<?php print_r('Father!'); print_r('Father!');
In the simplest case, this is what you should do, but if the phrase Father! starts to be used more and more often, and in different parts of the program, you'll have to repeat it everywhere. Then you'll face even more issues when it turns out that you need to change the phrase. This is a common scenario in development. We have to find all the places where the phrase Father! was used and make the necessary substitutions. There is one other way to do it. Instead of copying our expression, just create a variable containing this phrase.
<?php // greeting $greeting = 'Father!'; print_r($greeting); print_r("\n"); print_r($greeting);
$greeting = 'Father!' assigns the value
'Father!' to a variable named
$greeting. In PHP, variable names begin with a $ sign. As a result, the variable points to the data that was written to it.
Once the variable's been created, you can start using it. You put it in the places where we originally had our phrase written out in full. At runtime, the interpreter (the program that executes the PHP code), reaches the line
print_r($greeting); and replaces the variable with its contents, and then executes the code. As a result, the output of our program will be as follows:
Any set of valid characters can be used for a variable name, which includes letters of the English alphabet, numbers, and the
_. Note that you can't place a digit at the beginning of a name. Variable names are case-sensitive, which means that
heLLo are two different names and thus two distinct variables. Case is important in PHP, never forget it.
The number of variables you can create isn't limited in any way, large programs contain tens and hundreds of thousands of variable names:
<?php $greeting1 = 'Father!'; print_r($greeting1); print_r($greeting1); $greeting2 = 'Mother!'; print_r($greeting2); print_r($greeting2);
For the convenience of program analysis, it's customary to create variables as close as possible to where they're used.
Create a variable named
What Is Dead May Never Die!. Print its contents.
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.
A variable is a way to store information and name it for later use in code.