RegExp Pattern for checking for NO HTML Tags!

ppowell

I am having to use an existing FormValidator class to check form elements, and one of the things I must check is to see if someone entered tags in the string <>; if so, it must flag for that.

However, the catch is that, the way FormValidator class is written, I can't use this pattern:

/<[^>]+>/

because it needs to check for the pattern of the NEGATION of that for FormValidator class to work. In other words, it must match the pattern something like this:

! /<[^>]+>/

But the only way I can do this is to create a pattern and nothing more; no other code of any kind except the literal pattern formed in such a way to check for everything BUT a tag!

I also cannot use str_replace and strip out the tags; I can't use htmlentities and translate the tags.. the requirements are to FLAG the user if a tag is found but by NOT using the pattern to find one, but to ONLY use the pattern to find the NEGATION of finding one!!!

Mind bender, I know.

HELP!

Phil

dave420

If I understood your question, I'd help :-P Have you tried blowing on it?

ppowell

Yep, it worked!!!!

Ok, seriously, I got it from Google, although to be honest I simply do not understand the notation:

/^{(?!.*<[^>]+>)/}

????

Phil

Weedpacket

I wonder if(strip_tags($text)==$text) would check that there aren't any tags in $text?

bubblenut

Bit of a complicated one so sorry if I'm not quite right (not great on lookaheads)
Right; the slashes at the start and end are the delimiters (as I'm sure you knew already) the ^ means match at the start of the string then open parenthesis, this is the bit that will be returned into the third parameter of preg_match.
Now onto the hard bit.
?! is a negative lookahead, in this case it's just being used to negate the regex really. It's looking ahead at the following characters without including them in the return string (this is not really important in this case) and if the string exactly does not match the string it returns true.
HTH
Bubble

Weedpacket

Originally posted by ppowell
Yep, it worked!!!!

Ok, seriously, I got it from Google, although to be honest I simply do not understand the notation:

/^{(?!.*<[^>]+>)/}

????

Phil

It basically says "match the start of the string () only if it is not followed by (color=darkblue[/color]) something (.*) containing a tag (<[^>]+>) .

Pattern Syntax

dave420

/^{(?!.*<[^>]+>} )/

It's saying 'Match only a string that does not start with some/none characters before a tag', effectively matching a tag anywhere in the document, and returning a positive if no tags are found. Negative assertions rule 😉

Weedpacket

Well, the only part of the string that is actually matched is the very start. The difference can be significant.