正则表达式在Unicode上失败

Question

I'm trying to find the string "C#" in a text using php and reg exp.

I'm using

\bc\x{0023}\b

But doesn't work at all.

\bc\x{0023} 

works but that's not a solution for me

Any clue ?

Answer 1

It's because the escape sequence \\b means a word boundary. Word is defined according to the PHP manual as: " A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl "word". ".

Word boundary means the boundary between a word and a nonword. In otherwords, a between a character that is a word character and character is a not a word character. The problem is that # is not a word character. Thus, unless # is followed by a word character, #\\b will never match.

Perhaps you should define more clearly using character classes what you want. For example /\\bc#(?![az])/i (that is, C# that is not followed by az character range)