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PHP: Variable naming

$greeting is an example of a simple name, but not all names are that simple. Often, they're a combination of several words. For example, "user password". Different languages have different naming styles for variables.

There are three main variable naming conventions, which are sometimes combined. These conventions apply to variable names consisting of several words:

  • kebab-case — a hyphen separates the parts of the name. For example, my-super-var.
  • snake_case — an underscore is used as a separator. For example, my_super_var.
  • CamelCase — each word in the name is capitalized. For example, MySuperVar.
  • lowerCamelCase — each word is capitalized except the first. For example, mySuperVar.

PHP uses CamelCase and its variation lowerCamelCase, where the first letter of the first word is lowercase. We use lowerCamelCase for variables. This means that names are joined together, with all but the first word capitalized: $userName. With three words, it looks like this: $mySuperVariable.

Over time, by digging through other people's code, you'll develop the right concepts for naming.

Names should not only convey meaning, but also correspond to syntactic rules, which aren't usually checked by the language, but are still needed during development. Program writing in today's world is a team effort, and for better teamwork, code should be written in a unified style. Every language has its own rules. PHP has been in chaos for a long time. And the language itself is riddled with contradictions, and not only with names. You will encounter this in the following lessons and in real work. A coding standard, for PHP only appeared relatively recently, and everyone is striving to meet it one way or another. Standards describe multiple aspects. We recommend making a habit of looking at the standard and writing code according to it from the very beginning.

Fortunately, nowadays, you don't need to remember all the rules from the standard, because there are special programs that check the code automatically and report violations. These programs are called linters, and you'll start using them later when you have a little more experience.


Create two variables named "first number" and "second number" using lowerCamelCase. Write the number 1.10, to the first variable and -100 to the second. Print the product of the numbers written to the resulting variables.

The code will work with any name, and we only check the printed result, so the task is up to you.

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 coding standard is a set of syntactic and stylistic rules for writing code.

If you got stuck and don't know what to do, you can ask a question in our community