php - mb_substr_replace

			function mb_substr_replace($string, $replacement, $start, $length = null, $encoding = "UTF-8") {
				if (extension_loaded('mbstring') === true){
					$string_length = (is_null($encoding) === true) ? mb_strlen($string) : mb_strlen($string, $encoding);
					if ($start < 0) { $start = max(0, $string_length + $start); }
					else if ($start > $string_length) {$start = $string_length; }
					if ($length < 0){ $length = max(0, $string_length - $start + $length);  }
					else if ((is_null($length) === true) || ($length > $string_length)) { $length = $string_length; }
					if (($start + $length) > $string_length){$length = $string_length - $start;}
					if (is_null($encoding) === true) {  return mb_substr($string, 0, $start) . $replacement . mb_substr($string, $start + $length, $string_length - $start - $length); }
					return mb_substr($string, 0, $start, $encoding) . $replacement . mb_substr($string, $start + $length, $string_length - $start - $length, $encoding);
				}
				return (is_null($length) === true) ? substr_replace($string, $replacement, $start) : substr_replace($string, $replacement, $start, $length);
			}