$re = '~([\d:\h,]+ --> [\d:,]+)~';
$str = '1 00:00:30,304 --> 00:00:34,165 Our focus today is to share with you 2 00:00:34,165 --> 00:00:36,715 key components of preparing and submitting 3 00:00:36,715 --> 00:00:40,715 a warranty transaction...';
$subst = "";
$result = preg_replace($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