$re = '/[0-9]*\n[0-9: -,->]+\n(<[^<]+>){2}([^<]+)<\/font><\/b>/m';
$str = '1
00:00:07,133 --> 00:00:10,833
<b><font color=\'#ffd109\'>- It was ninety one years ago, today</font></b>
2
00:00:07,133 --> 00:00:10,833
<b><font color=\'#ffd109\'>Line two</font></b>
244
00:00:07,133 --> 00:00:10,833
<b><font color=\'#ffd109\'>Line three</font></b>';
$subst = "\2";
$result = preg_replace($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