note 55028 added to reference.pcre.pattern.syntax

Found a great expression that replaces a text url - http:/.... with <a href ="http://www..."> Although it works, I still don't understand how. If someone could explain this it would great to learn what amounts to me as a foreign language :-) Here is the expression: '%&quot;(.+)&quot;[\s]+((http|https|ftp|file)://[^\s]+?)(.*)%sU' $pcre = '%&quot;(.+)&quot;[\s]+((http|https|ftp|file)://[^\s]+?)(.*)%sU'; if ( preg_match( $pcre, $lines ) ){ $lines = preg_replace( $pcre, '<a href="$2" target="_top">$1</a>$4', $lines ); } else { $pcre = '%\b((http|https|ftp|file)://[^\s]+?)(.*)%U'; $lines = preg_replace( $pcre, '<a href="$1" target="_top">$1</a>$3', $lines ); } ---- Manual Page -- http://www.php.net/manual/en/reference.pcre.pattern.syntax.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+55028 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+55028&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+55028&report=yes Search -- http://master.php.net/manage/user-notes.php