public function longestCommonPrefix($otherStr)
{
$encoding = $this->encoding;
$maxLength = min($this->length(), \mb_strlen($otherStr, $encoding));
$longestCommonPrefix = '';
for ($i = 0; $i < $maxLength; $i++) {
$char = \mb_substr($this->str, $i, 1, $encoding);
if ($char == \mb_substr($otherStr, $i, 1, $encoding)) {
$longestCommonPrefix .= $char;
} else {
break;
}
}
return static::create($longestCommonPrefix, $encoding);
}