How can I merge this RegEx code

Question

I’ve written this regex code,

/.[^.]*$/ -> file extension

/\?.*/ -> removes everything ?paramternames in PHP

Current usage:

preg_replace('/\?.*/', '', preg_replace('/.[^.]*$/','',basename($_SERVER['REQUEST_URI'])))

How can I make it to a single preg_replace call, instead of these two, is there a way to merge the two RegExes into one single RegEx which does the job?

Can I posted expected output result? Yes.

http://localhost/books.php?tab=to_read

when I run this PHP code with two preg_replaces, I get "books", which I use to highlight in the menu to tell the user current page and menu highlight based on the page URI.

EDIT: There's nothing wrong with this code, it works. However, I want to merge the two regexes into one and only invoke one preg_replace.

what output after preg_replace('/.[^.]*$/','',basename($_SERVER['REQUEST_URI'])); ? — splash58
– splash58, Commented Jul 14, 2015 at 18:23

mario · Accepted Answer · 2015-07-14 18:31:20Z

5

Oftentimes you can just combine two patterns per alternation one|two.

In your case either the "file extension" or the query string might be absent, and they should be matched in the right order. Which is why you should optionalize both parts:

 preg_replace("~ (\.\w+)? (\?.*)?  $   ~x",
                    ↓       ↓      ↓    ↓
                  ".ext"  "?………"  END  readability flag

This ensures the .ext either directly precedes the query string, or spans the last characters itself. Likewise could the query string be optional, but still should match without preceding extension.

edited Jul 14, 2015 at 18:31

answered Jul 14, 2015 at 18:24

mario

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11 Comments

John Smith Over a year ago

WOW! This worked. Can you explain this regex in details, thanks?

John Smith Over a year ago

And it supports all types of extensions? Right? Thanks a lot.

Qix - MONICA WAS MISTREATED Over a year ago

Cool arrows. I need to remember those.

mario Over a year ago

@Qix Kinda got in in the habit lately. They're often mapped to AltGr+U / Y / I.

mario Over a year ago

@N000b101 Now I wouldn't call it bad. You're operating just on the REQUEST_URI here. If this was for a full IRI/URL it would likely mismatch domain names etc. Perhaps not relevant. However it would behave just the same as your original 2×preg_replace approach.

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