RE: [PHP] preg_match problem

> -----Original Message----- > From: Paul Novitski [mailto:paul@juniperwebcraft.com] > Sent: January 22, 2007 6:58 PM > To: PHP > Subject: Re: [PHP] preg_match problem > > At 1/22/2007 03:04 PM, Beauford wrote: > >I'm trying to get this but not quite there. I want to allow the > >following characters. > > > >A-Za-z0-9!@#$%&()*;:_.'/\ and a space. > > > >Is there a special order these need to be in or escaped somehow. For > >example, if I just allow _' the ' is fine, if I add the other > >characters, the ' gets preceded by a \ and an error is > returned. If I > >take the ' out of the sting below it works fine, I get no errors > >returned. I am also using stripslashes on the variable. > > > >This is my code. (although I have tried various things with > it trying > >to get it right) > > > >if(preg_match("/^[-A-Za-z0-9!@#%&\(\)\*;:_.\'\$ ]+$/", $string)) { > > > Please read this page: > > Pattern Syntax -- Describes PCRE regex syntax > http://ca.php.net/manual/en/reference.pcre.pattern.syntax.php > > specifically the section on character classes: > http://ca.php.net/manual/en/reference.pcre.pattern.syntax.php# > regexp.reference.squarebrackets > > In PREG there are few characters that you need to escape in a > character class expression: > > 1) ^ must be escaped (\^) if it's the first character (it > negates the match when it's unescaped in the first position). > > 2) ] must be escaped (\]) unless it's the first character of > the class (it closes the class if it appears later and is not > escaped). > > 3) \ must be escaped (\\) if you're referring to the > backslash character rather than using backslash to escape > another character. > > 4) Control codes such as \b for backspace (not to be confused > with \b which means word boundary outside of a character class). > > > In addition, you may need to escape certain characters in PHP if > you're expressing the RegExp pattern in a quoted string, such as > single or double quotes (whichever you're using to quote the pattern): > > '[\'"]' escape the apostophe > "['\"]" escape the quotation mark > > Those are PHP escapes -- by the time PREG sees the pattern, the PHP > compiler has rendered it to: > > ['"] > > And then of course there's the complication that both PREG and PHP > use the backslash as the escape character, so the pattern: > > [\\] escape the backslash > > must be expressed in PHP as: > > [\\\\] escape the escape and the backslash > > Interestingly, PHP compiles both \\\ and \\\\ as \\, go figure. I > use \\\\ to escape both backslashes to maintain some semblance of > logic and order in these eye-crossing expressions. > > Because PHP requires quotes to be escaped, I find it easier to write > & debug patterns in PHP if I express them in heredoc where quoting > and most escaping is unnecessary: > > $sPattern = <<<_ > ['"\\\\] > _; > > becomes the PREG pattern ['"\\]. > > > So to address your character class: > > >A-Za-z0-9!@#$%&()*;:_.'/\ and a space. > > I'd use the pattern: > > [A-Za-z0-9!@#$%&()*;:_.'/\\ ] > > where the only character I need to escape is the backslash itself. > > In PHP this would be: > > $sPattern = '[A-Za-z0-9!@#$%&()*;:_.\'/\\\\ ]'; > (escaped apostrophe & blackslash) > or: > $sPattern = "[A-Za-z0-9!@#$%&()*;:_.'/\\\\ ]"; > (escaped blackslash) > or: > $sPattern = <<<_ > [A-Za-z0-9!@#$%&()*;:_.'/\\\\ ] > _; > (escaped blackslash) I've probably read 100 pages on this, and no matter what I try it doesn't work. Including all of what you suggested above - is my PHP possessed? if(preg_match("/^[A-Za-z0-9!@#$%&()*;:_.'/\\ ]+$/", $string)) { gives me this error. Warning: preg_match() [function.preg-match]: Unknown modifier '\' in /constants.php on line 107 So if If you wouldn't mind, could you show me exactly what I need right from the beginning and explain why it works. i.e. if(preg_match(what goes here", $string)) { Echo "You got it";