Calculating percentage changes without dividing by zero

Question

I have the following the PHP that I am using to calculate percentage decreases or increases:

function CalculatePercentageIncrease( $nLastMonthPeriod, $nCurrentPeriod ) {
    if ( !is_numeric( $nLastMonthPeriod ) || !is_numeric( $nCurrentPeriod ) )
        return 0;

    if ( $nLastMonthPeriod == 0 )
        return 0;

    $nLastMonthPeriod = intval( $nLastMonthPeriod );
    $nCurrentPeriod = intval( $nCurrentPeriod );

    $nDifference = ( ( ( $nCurrentPeriod - $nLastMonthPeriod ) / $nLastMonthPeriod ) * 100 );

    return round( $nDifference );
}

The problem that I am wondering about is if $nLastMonthPeriod is 0 and $nCurrentPeriod is 10 then should it be returning 100 and not 0?

Answer 1

if $nLastMonthPeriod is 0 and $nCurrentPeriod is 10 then should it be returning 100 and not 0?

Thats what you coded ...

  if ( $nLastMonthPeriod == 0 )
        return 0;

did you mean?

  if ( $nLastMonthPeriod == 0 )
       if ($nCurrentPeriod>0)
          return 100; //whatever you want
       else
          return 0;