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PHP: Сигнатура функции

The pow(), function, which raises a number to any power, takes two parameters: which number to raise and to what power to raise it to. If you call pow() without parameters, PHP outputs the following: PHP Warning: pow() expects exactly 2 parameters, 0 given in php shell code on line 1. The interpreter has told you that the function expects 2 parameters, and that you called it without parameters.

Whoever created the pow(), function made it a function with two mandatory parameters, so it can't be called with any other number of parameters.

Moreover, the parameters of pow() can only be numbers. Attempting to pass, for example, a string to it will result in the following error: PHP Warning: A non-numeric value encountered in php shell code on line 1. The result of this function call will also always be a number.

Other functions may have different numbers of parameters and different types of parameters. For example, there may be a function that takes three parameters: a number, a string, and another number.

How do we know how many parameters the pow function needs and what sort of result it'll return? We've taken a look at this function's signature. The signature defines the input parameters and their types, as well as the output parameter and its type. You can read about the pow function in the official PHP documentation. In the "description" section, you can see this this text:

pow ( number $base , number $exp ) : number

Returns base raised to the power of exp.

This is a function signature and a short explanation.

The information is deciphered as follows:
- the function is called pow
- the function takes two parameters: a number (base) and a number (exp)
- the function returns a number (number)
- the function returns base raised to the power of exp

Parameters can only be passed in the order they're given in the signature.

Any function will always return only one value. This restriction exists at language level and cannot be broken.


Now it's your turn, look at the signature of a function in the documentation and work out how to use it. Now it's your turn to find the function signature in the documentation and figure out how to use it.

In PHP, there's a function called ucfirst(). Study its signature at

Write a program that uses ucfirst() with the variable $text and displays the result. The value of the $text variable is already defined.

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 function signature is a formal description of the types of arguments and the type of return value of a function.

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