How to Negate a Number in PHP?

In PHP, you can negate a number (i.e. convert a positive number to negative, and a negative to positive) in the following ways:

• Using Negation Operator;
• Using Arithmetic Operators.

Please note that in PHP, when negating 0, the result is always 0.

Using Negation Operator

You may negate a number using the negation operator (-) like so:

-n

This would convert a positive number to a negative number, and a negative number to a positive number. For example, you can use it in the following way:

function negate(int|float $num): int|float
{
    return -$num;
}

var_dump(negate(1234)); // -1234
var_dump(negate(-1234)); // 1234

var_dump(negate(0)); // 0
var_dump(negate(-0)); // 0

Using Arithmetic Operators

You may convert a positive number to negative or vice versa by simply multiplying it by -1:

n * -1

Similarly, you may also divide the number by -1 to negate it:

n / -1

You could use either of these, for example, like so:

function negate(int|float $num): int|float
{
    return $num * -1;
}

var_dump(negate(1234)); // -1234
var_dump(negate(-1234)); // 1234

var_dump(negate(0)); // 0
var_dump(negate(-0)); // 0

function negate(int|float $num): int|float
{
    return $num / -1;
}

var_dump(negate(1234)); // -1234
var_dump(negate(-1234)); // 1234

var_dump(negate(0)); // 0
var_dump(negate(-0)); // 0

As an alternative to dividing and multiplying by -1, you may subtract the number from 0 instead:

0 - n

For example, you could use it in the following way:

function negate(int|float $num): int|float
{
    return 0 - $num;
}

var_dump(negate(1234)); // -1234
var_dump(negate(-1234)); // 1234

var_dump(negate(0)); // 0
var_dump(negate(-0)); // 0