A function that generates an array of hex colors that forms a gradient, starting from a hex color and ending with another hex color. The number of gradient steps can also be defined.

function Gradient($HexFrom, $HexTo, $ColorSteps)
{
        $FromRGB['r'] = hexdec(substr($HexFrom, 0, 2));
        $FromRGB['g'] = hexdec(substr($HexFrom, 2, 2));
        $FromRGB['b'] = hexdec(substr($HexFrom, 4, 2));
       
        $ToRGB['r'] = hexdec(substr($HexTo, 0, 2));
        $ToRGB['g'] = hexdec(substr($HexTo, 2, 2));
        $ToRGB['b'] = hexdec(substr($HexTo, 4, 2));
       
        $StepRGB['r'] = ($FromRGB['r'] - $ToRGB['r']) / ($ColorSteps - 1);
        $StepRGB['g'] = ($FromRGB['g'] - $ToRGB['g']) / ($ColorSteps - 1);
        $StepRGB['b'] = ($FromRGB['b'] - $ToRGB['b']) / ($ColorSteps - 1);
       
        $GradientColors = array();
       
        for($i = 0; $i <= $ColorSteps; $i++)
        {
                $RGB['r'] = floor($FromRGB['r'] - ($StepRGB['r'] * $i));
                $RGB['g'] = floor($FromRGB['g'] - ($StepRGB['g'] * $i));
                $RGB['b'] = floor($FromRGB['b'] - ($StepRGB['b'] * $i));
               
                $HexRGB['r'] = sprintf('%02x', ($RGB['r']));
                $HexRGB['g'] = sprintf('%02x', ($RGB['g']));
                $HexRGB['b'] = sprintf('%02x', ($RGB['b']));
               
                $GradientColors[] = implode(NULL, $HexRGB);
        }
        return $GradientColors;
}
 
$Gradients = Gradient("FF5B5B", "FFCA5B", 32);
foreach($Gradients as $Gradient)
{
        echo "<div style=\"background-color: #".$Gradient."; width: 100px; height: 25px;\"></div>";
}