ColorConverter.php

<?php
/**
* ColorConverter
* @author eDroid
* @link https://edroidthedev.com
*/
class ColorConverter {
  /**
	* Hex to RGB
	*
	* @param string $hex The hex value to convert. (ex. #ffffff)
	*/
  public function to_rgb(string $hex): array {
      $h = substr($hex, -6);
      return [hexdec(substr($h, 0, 2)), hexdec(substr($h, 2, 2)), hexdec(substr($h, 4, 2))];
  }
  /**
	* RGB to Hex
	*
	* @param array $rgb The rgb value to convert. (ex. Array([0] => 255, [1] => 255, [2] => 255))
	*/
  public function to_hex(array $rgb): string {
      return "#" . dechex($rgb[0]) . dechex($rgb[1]) . dechex($rgb[2]);
  }
}
?>

Example.php

<?php
require_once('ColorConverter.php');
$converter = new ColorConverter;

$hex = "#BADA55";
$rgb = array(186, 218, 85);

print_r($converter->to_rgb($hex)); // [186, 218, 85]

print_r($converter->to_hex($rgb)); // #bada55
?>