code: protected static function hexToUnicode($char){
  
  		if(!is_string($char) || !preg_match('(^[0-9a-f]{2,6}$)i', $char)){
  			throw new \InvalidArgumentException('$char must be one single unicode character as hex string');
  		}
  
  		return mb_convert_encoding('&#x'.strtolower($char).';', 'UTF-8', 'HTML-ENTITIES');
  
  	}
docs: get the unicode character of a unicode hex string
  
  @param  string $char unicode hex representation (e.g. "263a")
  @return string       single character encoded as UTF-8