color generator

lights.php

<?php
// 3 ranges, values from 0 to 254 (0:ff) each
//cycle all possible values (0:0:0 to ff:ff:ff)

//we have N positions
// each position will get a color at a time
// position 0 = 0:0:0
// position 1 = 0:0:1
// ...
// position n-1 = color combination that is able to fit
// clear first position and replace with second, swapping the rest of the values until the las position is empty
// add the next color in sequence at the last position

function nextColor($red, $green, $blue, $step = 25)
{
    $blue += $step;

    if ($blue > 255) {
        $blue = 0;
        $green += $step;
    }

    if ($green > 255) {
        $green = 0;
        $red += $step;
    }

    if ($red > 255) {
        $red = 0;
    }

    return [$red, $green, $blue];
}

$arrPositions = [];
$numPositions = 5;
$currRun = 0;
$totalRuns = 1000;

//INITIALIZE
$red = 0;
$green = 0;
$blue = 0;
$format = '#%02X%02X%02X';

$arrPositions[] = sprintf($format, $red, $green, $blue);
for ($i = 1; $i < $numPositions; $i++) {
    list($red, $green, $blue) = nextColor($red, $green, $blue);
    $arrPositions[] = sprintf($format, $red, $green, $blue);
}

print_r($arrPositions);

for ($currRun = 0; $currRun < $totalRuns; $currRun++) {
    array_shift($arrPositions);
    list($red, $green, $blue) = nextColor($red, $green, $blue);
    $arrPositions[] = sprintf($format, $red, $green, $blue);
    print_r($arrPositions);
}