PHP regexp for /prefix/action(/id)

I'm trying to build a regexp that would match both strings:

/prefix/action

and

/prefix/action/43

but not

/prefix/action/

or

/prefix/action43

where 43 can be anything like [0-9]+, only if preceded by a slash

I also want to capture the number (not the slash), if any, as a named group.

~/prefix/action/?(?P<itemID&开发者_开发知识库gt;[0-9]+)?~

This expression does match, except for a condition that numbers must be preceded by a slash, all my attempts at adding lookahead or lookbehind assertions failed on this one.

I do understand that with additional external processing the task can be solved, but I'm looking for a regexp solution only. Thank you for understanding.

Your suggestions are greatly appreciated.

Solved by:

~/prefix/action(?:/(?P<itemID>[0-9]+))?~

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How about making both the / and the following number optional?

^/prefix/action(?:/[0-9]+)?$

To capture the optional number in a named group add (?P<itemID>...) around the number regex:

^/prefix/action(?:/(?P<itemID>[0-9]+))?$

Also note that I've added start and end anchors, which were missing in your regex. Without them you'll get a match if you have a sub-string of the input that matches the regex.