Let’s learn some important terms before moving forwards. An operation sign like + is called an operator. It’s just a symbol that produces a certain operation. Later you’ll learn that there are other operators in PHP, than just arithmetic ones.


print_r(8 + 2);

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

In case of addition there’re two operands: one on the left, one on the right from +. Operators that require two operands are called binary. If you skip at least one operand, like so 3 + ;, the program will exit with an error.

There are also unary operations (with one operand) and even ternary (with three operands)!

Symbols + and - are used not only as operators. As far as negative numbers are concerned, the minus sign becomes part of the number:


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

The plus sign can work in the same way:


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


Write a program that calculates the difference between 6 and -81, and prints the result to screen.


  • Arithmetic operator — addition, subtraction, multiplication, division.

  • Operator — special symbol that creates an action. For example, + creates addition.

  • Operand — that what is being used with an operator. 3 * 6: here 3 and 6 are operands.

  • Unary operation — operation that requires one operand.

  • Binary operation — operation that requires two operands.

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