RainbowLetters

<?php
//1st - take input; str to int; int to hex
$text = $_GET['text'];
$red=dechex(intval($_GET['red']));
//var_dump($red)int - hex;
$green=dechex(intval($_GET['green']));
$blue=dechex(intval($_GET['blue']));
$nth=$_GET['nth'];
//2nd - valid RGB
if(strlen((string)$blue)==1){
    $blue.='0';
}
if(strlen(strval($red))==1){
    $red.='0';
}
if(strlen(strval($green))==1){
    $green.='0';
}
$validRGB=strtolower("#".$red.$green.$blue);
//var_dump($validRGB);
$result="<p>";
for($i=0; $i<strlen($text); $i++){

    if(($i+1)%$nth==0){
        $result.= "<span style=\"color: $validRGB\">".htmlspecialchars($text[$i])."</span>";
    }else{
        $result.= htmlspecialchars($text[$i]);
    }
}
$result .= "</p>";
    echo $result;