Functions that can generate a sequence of ROYGBIV text for HTML or Minecraft using it's formatting codes.

roygbiv_function.php

<?php

/**
 *
 * @param string $text
 * @param int    $amount
 *
 * @return array
 *
 */
function generate_ROYGBIV_HTML(string $text, int $amount = -1): array{
        $return = [];
        $colors = ["#FF0000", "#FF7400", "#FFD400", "#00FF00", "#00FFEC", "#0000FF", "#D800FF"];
        $amount = ($amount < 1) ? strlen($text) : $amount;
        $split = str_split($text);

        for($i = 0; $i < $amount; ++$i){
                $out = "";
                $loop = 0;
                foreach($split as $part){
                        $out .= "<p style='color: " . $colors[$loop++] . "'>" . $part . "<p/>";
                        if($loop > (count($colors) - 1)){
                                $loop = 0;
                        }
                }
                $color = array_shift($colors);
                $colors[] = $color;
                $return[] = $out;
        }

        return $return;
}

/**
 *
 * @param string $text
 * @param int    $amount
 *
 * @return array
 *
 */
function generate_ROYGBIV_MC(string $text, int $amount = -1): array{
        $return = [];
        $colors = ["&c", "&6", "&e", "&a", "&b", "&9", "&5"];
        $amount = ($amount < 1) ? strlen($text) : $amount;
        $split = str_split($text);

        for($i = 0; $i < $amount; ++$i){
                $out = "";
                $loop = 0;
                foreach($split as $part){
                        $out .= $colors[$loop++] . $part;
                        if($loop > (count($colors) - 1)){
                                $loop = 0;
                        }
                }
                $color = array_shift($colors);
                $colors[] = $color;
                $return[] = $out;
        }

        return $return;
}