$re = '/(?<!:/)(/sports/[a-z0-9/.:-]*[0-9.]+cms)/m';
$str = '/sports/cricket/ipl/top-stories/kxip-vs-csk-shane-watson-faf-du-plessis-infuse-life-into-csks-ipl-campaign-shape-confidence-boosting-win-over-kxip/articleshow/78481088.cms
/sports/football/epl/top-stories/epl-manchester-united-humiliated-as-mourinhos-spurs-win-6-1-at-old-trafford/articleshow/78481304.cms
https://sports/football/epl/top-stories/epl-manchester-united-humiliated-as-mourinhos-spurs-win-6-1-at-old-trafford/articleshow/78481304.cms';
$subst = "https://\1";
$result = preg_replace($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