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PHP: Operators

Before we move on, let's take a look at the basic terminology. An operation sign, such as +, is called an operator. Operators perform operations on certain values, which are called operands. The operators themselves are usually represented by one or more characters,, and occasionally by a word. Most of the operators are identical to those you'll have seen in math class.


print_r(8 + 2);

In this example + is an operator, and the numbers 8 and 2 are operands.

When it comes to addition, we have two operands: one to the left of the + sign and one to the right. Operations with two operands are called binary operations. If at least one operand is omitted, e.g., 3 + ;, the program will end with a syntax error.

Operations can be more than just binary, they can also be unary (one operand), and even ternary (three operands). Moreover, operators may look the same but denote different operations. The symbols + and - are used as more than just operators. When it comes to negative numbers, the minus sign becomes part of the number:


print_r(-3); // => -3

Above is an example of applying a unary operation to the number 3. The minus operator before the three tells the interpreter to take the number 3 and find the opposite, which is -3.

This can be a bit confusing because -3 is both a number in itself and an operator with an operand, but this is just how programming languages are structured.


// Same as 4 - 3
print_r(4 + -3); // => 1

The same goes for the plus sign:


print_r(+3); // => 3
print_r(1 + +3); // => 4


Write a program that calculates the difference between the numbers 6 and -81 and displays the answer on the screen.

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.

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I've read the lessons but nothing is clear 🙄

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  • Arithmetic operations include addition, subtraction, multiplication and division.

  • A unary operation is an operation with one operand. For example, -3 is a unary operation to get the opposite of three.

  • A binary operation is an operation with two operands. For example, 3 + 9.

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