Regex: Replace unknown number of occurances after a given marker - php

Question

I am trying to figure out a way of replacing a / with - in the GET part of a href tag in a html file looking like this:
blah blah <a href="aaaaa/aaaaa/aaaaa/?q=43/23"> blah blah <a
href="aaaaa/aaaaa/aaaaa/?q=43/11/1"> blah blah blah
So basically I'm looking to make the two URLs end with ?q=43-23 and ?q=43-11-1 respectively.
How can I do this with a preg_replace? I can obviously get the 43/23 to be 43-23 with
/(\?.+?)\/(.+?)$/is
And I can get 43/11/1 to be 43-11-1 with
/(\?.+?)\/(.+?)\/(.+?)$/is
But how can I do this in a single regex taking into account that there may be an unlimited number of slashes after the ?. Any suggestions or someone who can point me in the right direction?

Answer 1

I think it could be easy for your content;
print preg_replace_callback('~\?q=([^&"]*)~', function($m) {
return '?q='. str_replace('/', '-', $m[1]);
}, $s);
// for PHP < 5.3.0
print preg_replace_callback('~\?q=([^&"]*)~', create_function(
'$m', 'return "?q=". str_replace("/", "-", $m[1]);'
), $s);
Out;
blah blah <a href="aaaaa/aaaaa/aaaaa/?q=43-23"> blah blah <a
href="aaaaa/aaaaa/aaaaa/?q=43-11-1"> blah blah blah
blah blah blah blah blah blah blah

Answer 2

This is not the simplest search and replace because of how regex engines handle repeated capture groups. Applying repeated capture group principles, you can use the regex to capture the repeating group and then do a simple string replace.
preg_replace_callback('/
( # start capture
\? # question mark
.+? # reluctantly capture all until...
) # end capture
( # start capture
(?: # start group (no capture)
\/ # ...a literal slash
.+? # reluctantly capture all until...
) # end group
+ # repeat capture group
) # end capture
( # start capture
\b # ...a word boundary
) # end capture
/isx', function ($matches) {
return $matches[1] . str_replace('/', '-', $matches[2]) . $matches[3];
}, $str));
You do the string replace on the second match which is the repeated group capture. The word boundary at the end is necessary, but it can be replaced with something more sensible or correct such as " (if you know the URL ends here), or even ("|').

Answer 3

You can use this regex to match an unlimited amount of (slash) levels after the query parameter q=.
// Using tilde delimiters because hash signs are interpreted as comments here :)
~q=((?:[^/]+|/|)*)$~i
For example with the string "aaaaa/aaaaa/aaaaa/?q=43/11/1/5/10" the first captured group will contain 43/11/1/5/10.
Afterwards you can do the following to replace slashes with hyphens:
<?php str_replace( '/', '-', $string );