$re = '/[^\p{Zs}\p{P}]*?ह[^\p{Zs}\p{P}]*/u';
$str = 'तरह के लाभ मिलते हैं';
$subst = "<b>$0</b>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php