public function countSubstr($substring, $caseSensitive = true)
{
if ($caseSensitive) {
return \mb_substr_count($this->str, $substring, $this->encoding);
}
$str = \mb_strtoupper($this->str, $this->encoding);
$substring = \mb_strtoupper($substring, $this->encoding);
return \mb_substr_count($str, $substring, $this->encoding);
}