RE: [PHP] RegExp question: how to add a number?

> -----Original Message----- > From: Andre Polykanine [mailto:andre@oire.org] > Sent: 14 October 2010 21:42 > > Hi everyone, > I hope you're doing well (haven't written here for a long time :-)). > The question is as follows: I have a regexp that would do the > following. If the string begins with "Re:", it will change the > beginning to "Re[2]:"; if it doesn't, then it would add "Re:" at the > beginning. But (attention, here it is!) if the string starts with > something like "Re[4]:", it should replace it by "Re[5]:". > Here's the code: > > $start=mb_strtolower(mb_substr($f['Subject'], 0, 3)); > if ($start=="re:") { > $subject=preg_replace("/^re:(.+?)$/usi", "re[2]:$1", > $f['Subject']); > } elseif ($start=="re[") { > // Here $1+1 doesn't work, it returns "Re[4+1]:"! > $subject=preg_replace("/^re\[(\d+)\]:(.+?)$/usi", "re[$1+1]:$2", > $f['Subject']); > } else { > $subject="Re: ".$f['Subject']; > } > > I know there actually exists a way to do the numeral addition > ("Re[5]:", not "Re[4+1]:"). > How do I manage to do this? This looks like a job for the "e" modifier (see http://php.net/manual/en/reference.pcre.pattern.modifiers.php, and example #4 at http://php.net/preg_replace). Something like: $subject = preg_replace("/^re\[(\d+)\:](.+?)$/eusi", "'re['.(\\1+1).']:\\2'", $f['Subject']); Cheers! Mike -- Mike Ford, Electronic Information Developer, Libraries and Learning Innovation, Leeds Metropolitan University, C507 City Campus, Woodhouse Lane, LEEDS,  LS1 3HE,  United Kingdom Email: m.ford@leedsmet.ac.uk Tel: +44 113 812 4730 To view the terms under which this email is distributed, please go to http://disclaimer.leedsmet.ac.uk/email.htm