Excluding certain characters when using the period

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I'd like to be able to allow only certain BBCodes in my forum.  To do so I am trying to use regular expressions to parse all the bbcode and removing the unwanted codes.

 

So far I have the expression that matches any simple bbcode

#\[(.+?)\](.+?)\[/\\1\]#is

 

However I'm not sure how to exclude the characters I want to keep (b, i, u a and s) from this expression.

 

Is it possible to exclude characters with a dot match.

[Adam]

You wouldn't use the dot character in this case, you'd just say like 'any character except these':

 

[^buias]+

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Thanks

 

That works for single character tags and I managed to work out how to match tags longer than one character as well.