[RESOLVED] checking to see if a number is a multiple of another number

[Desbrina]

I have this code

if ($row['amount'] == 5 || $row['amount'] == 10 || $row['amount'] == 15 || $row['amount'] == 20 || $row['amount'] == 25)
   			$perrow = 5;
		elseif ($row['amount'] == 4)
   			$perrow = 4;
		elseif ($row['amount'] == 3 || $row['amount'] == 6)
			$perrow = 3;
		else
			$perrow = 5;

which although works fine, its a pain adding a new value every time $row['amount'] gets bigger

is there a way of checking to see if $row['amount'] is a multiple of a number

[trevorsg]

function checkMultiple($num, $multiple) //returns true if $multiple is a multiple of $num
{
  $answer = ($num % $multiple === 0) ? true : false;
  return $answer;
}

Is that what you need?

[bradgrafelman]

Just to explain what trevorsg is suggesting...

Do some (simple?) math; the % or 'modulo' operator gives you the remainder when dividing, e.g. "7 % 3" is 1, since 7/3 is 2 with 1 as the remainder. Thus, if "x % 5" is 0, where 'x' is any number, then you know that 5 evenly divides into 'x' (or that 'x' is a multiple of 5).

[Desbrina]

thanks got it working with this

if (($row['type'] == "puzzle") and $row['amount'] == 15)
$perrow = 3;
elseif (($row['amount'] % 5) == 0)
$perrow = 5;
elseif (($row['amount'] % 4) == 0)
$perrow = 4;
elseif (($row['amount'] % 3) == 0)
$perrow = 3;
elseif (($row['amount'] % 2) == 0)
$perrow = 2;
elseif (($row['amount'] % 1) == 0)
$perrow = 1;
else
$perrow = 5;

[laserlight]

Incidentally, if $row['amount'] is an integer then ($row['amount'] % 1) == 0 is always true.

[Desbrina]

for some reason if i didn't have that then if amount = 6 then $perrow ended up as 5

[laserlight]

for some reason if i didn't have that then if amount = 6 then $perrow ended up as 5

Yes, that is what would happen. The thing is, you have unreachable code (i.e., the else branch).

Consequently, you should remove that unreachable code:

if ($row['type'] == 'puzzle' && $row['amount'] == 15)
    $perrow = 3;
elseif (($row['amount'] % 5) == 0)
    $perrow = 5;
elseif (($row['amount'] % 4) == 0)
    $perrow = 4;
elseif (($row['amount'] % 3) == 0)
    $perrow = 3;
elseif (($row['amount'] % 2) == 0)
    $perrow = 2;
else
    $perrow = 1;

Alternatively, you could use a loop:

if ($row['type'] == 'puzzle' && $row['amount'] == 15) {
    $perrow = 3;
} else {
    for ($i = 5; $i > 0; --$i) {
        if ($row['amount'] % $i == 0) {
            $perrow = $i;
            break;
        }
    }
}