RGB to HSV in PHP

Thoroughly tested and compressed, this is the function I'm going to stick with for converting RGB to HSV:

function RGBtoHSV($r,$g,$b) {
  $r=($r/255); $g=($g/255); $b=($b/255);
  $maxRGB=max($r,$g,$b); $minRGB=min($r,$g,$b); $chroma=$maxRGB-$minRGB;
  if($chroma==0) return array('h'=>0,'s'=>0,'v'=>$maxRGB);
  if($r==$minRGB)$h=3-(($g-$b)/$chroma);
  elseif($b==$minRGB)$h=1-(($r-$g)/$chroma); else $h=5-(($b-$r)/$chroma);
  return array('h'=>60*$h,'s'=>$chroma/$maxRGB,'v'=>$maxRGB);
} 

Example:

Example using color "DarkSalmon":

echo '<pre><code>'. print_r( RGBtoHSV(233,150,122), true ) .'</code></pre>';

...returns:

Array
(
    [h] => 15.135135135135
    [s] => 0.47639484978541
    [v] => 0.91372549019608
)

I did it like this

function convertRgbToHsv($rgb)
{

    $r = (int)substr($rgb, 0, 3) / 255;
    $g = (int)substr($rgb, 3, 3) / 255;
    $b = (int)substr($rgb, 6, 3) / 255;

    $max = max($r, $g, $b);
    $min = min($r, $g, $b);
    $delta = $max - $min;

    if (!$delta) {
        $h = 0;
    } else if ($r === $max) {
        $h = 60 * ((($g - $b) / $delta) % 6);
    } else if ($g === $max) {
        $h = 60 * ((($b - $r) / $delta) + 2);
    } else {
        $h = 60 * ((($r - $g) / $delta) + 4);
    }

    $s = !!$max ? $delta / $max : 0;

    $v = $max;

    $hsv = array("h" => $h, "s" => $s, "v" => $v);

    return $hsv;
}

Link to reference material here