A regular expression to exclude a word/string

Question

I have a regular expression as follows:

^/[a-z0-9]+$ 

This matches strings such as /hello or /hello123.

However, I would like it to exclude a couple of string values such as /ignoreme and /ignoreme2.

I've tried a few variants but can't seem to get any to work!

My latest feeble attempt was

^/(((?!ignoreme)|(?!ignoreme2))[a-z0-9])+$ 

Any help would be gratefully appreciated :-)

Answer 1

Here's yet another way (using a negative look-ahead):

^/(?!ignoreme|ignoreme2|ignoremeN)([a-z0-9]+)$  

Note: There's only one capturing expression: ([a-z0-9]+).

Answer 2

This should do it:

^/\b([a-z0-9]+)\b(?<!ignoreme|ignoreme2|ignoreme3) 

You can add as much ignored words as you like, here is a simple PHP implementation:

$ignoredWords = array('ignoreme', 'ignoreme2', 'ignoreme...');  preg_match('~^/\b([a-z0-9]+)\b(?<!' . implode('|', array_map('preg_quote', $ignoredWords)) . ')~i', $string);