Question

How can it be that this regular expression also returns strings that have a _ underscore as their last character?

It should only return strings with alphabetical characters, mixed lower- and uppercase.

However, the regular expression returns: 'action_'

 $regEx = '/^([a-zA-Z])[a-zA-Z]*[\S]$|^([a-zA-Z])*[\S]$|^[a-zA-Z]*[\S]$/';

Answer 1

The [\S] will match everything that is not whitespace, including underscore.

Also, your expression is very odd!

If you want a string that only contains letters, then use ^[a-zA-Z]*$ or ^[a-zA-Z]+$ (depending on if blank is allowed or not).

If you’re trying to do something else, you will need to expand on what that is.