PHP regex to parse a string of the form {string}\{string}

Question

As per title I need to parse string of the form string_1\string_2 as in a string followed by a backslash then by another string with the following requirements:

• if string_1 and string_2 are present, break them into two tokens: string_1 and \string_2
• if only string_1 is present, return it
• if \string_2 is present but nothing behind the backslash, don't match anything.

So far I've come up with this :

^([\w\s]*)((?!\\\).*)

but the last character in string_1 keeps 'leaking' through and going to string_2 right before the backslash.

Is there a way to fix that? Or any other alternative regex? The following regex does helps with the leaking but it break the third requirement.

^([\w\s]*).((?!\\\).*)

In order to make sure this question is not too localized, note that this could help parse a subset of latex when you have a string coming before say \section{section title comes here {*}}.

Answer 1

I think this is the regex you're looking for:

/^([^\\]+)(\\.+)?/

The first group is a "non-\" of at least 1 character, followed by optional "\" and anything else.