Detecting negative numbers

if ($profitloss < 0)
{
   echo "The profitloss is negative";
}

Edit: I feel like this was too simple an answer for the rep so here’s something that you may also find helpful.

In PHP we can find the absolute value of an integer by using the abs() function. For example if I were trying to work out the difference between two figures I could do this:

$turnover = 10000;
$overheads = 12500;

$difference = abs($turnover-$overheads);

echo "The Difference is ".$difference;

This would produce The Difference is 2500.