Apache2 rewrite returns filename extension - mod-rewrite

Question

I really don't understand where I'm doing wrong. I'm trying to apply a rule to
http://localhost/prezzo/account/1
so that it is rewritten as
http://localhost/prezzo/account/test.php?user=1
I'm using UniformServer as WAMP. I placed the .htaccess file in the subfolder I'm working on (prezzo/account/) with the following rule:
RewriteEngine On
RewriteRule (\w+)/?$ test.php?user=$1 [L]
htaccess tester reports that the rule is applied correclty.
But when I go to the URL http://localhost/prezzo/account/1 and test.php is loaded - which contains simply
<?php
echo $_GET['user'];
?>
it returns the string "php" instead of "1".
If I try with
RewriteRule ^prezzo/account/(\w+)/?$ prezzo/account/test.php?user=$1 [L]
I get 404 not found although htaccess tester reports that the rule is applied correctly and the URL is rewritten as
http://localhost/prezzo/account/test.php?user=1
that if I copy/paste in the address bar it works.

Answer 1

But when I go to the URL http://localhost/prezzo/account/1 and test.php is loaded [...] it returns the string "php" instead of "1".
Yes, this is expected with the rule as posted.
This appears to work in the "htaccess tester" because that tool only makes a single pass through the file, which is not how a real server works.
RewriteRule (\w+)/?$ test.php?user=$1 [L]
When you request /prezzo/account/1 then...
The request is rewritten to test.php?user=1
The L flag causes the rewrite engine to start over using the rewritten URL (test.php?user=1) as input to the next round of processing.
The request is rewritten to test.php?user=php since the regex (\w+)/?$ captures the php part of test.php. (The \w shorthand character class excludes dots and the regex is not anchored.)
The L flag causes the rewrite engine to start over using the rewritten URL (test.php?user=php) as input to the next round of processing.
The request is rewritten to test.php?user=php (again).
Since the URL has passed through unchanged the rewriting process stops and the request is finally rewritten to /test.php?user=php.
Solution A - Use the END flag
One solution is to simply use the END flag (Apache 2.4) instead of L to prevent the rewriting engine from "looping". It will stop as soon as the directive is processed. For example:
RewriteRule (\w+)/?$ test.php?user=$1 [END]
Solution B - Make regex more specific
The other solution (or as well as) is to make the regex more specific, so that it doesn't match test.php. ie. Only match the URL format you are expecting.
The regex (\w+)/?$ would seem to be too generic, as it is basically just matching the last group of letters/numbers on the URL-path. If you only want to match digits (a "user-id") then you could make the regex more restrictive and match only digits instead.
You should also anchor the regex at the start, so that it matches a whole path segment, rather than just capturing the last part that matches. In fact, simply anchoring the above regex would have also resolved this, since test.php would have failed to match because \w does not match dots.
For example:
RewriteRule ^(\d+)/?$ test.php?user=$1 [L]
This will match digits only in the last path segment.
If I try with
RewriteRule ^prezzo/account/(\w+)/?$ prezzo/account/test.php?user=$1 [L]
I get 404 not found although htaccess tester reports that the rule is
applied correctly and the URL is rewritten
If the .htaccess file is located in the /prezzo/account subdirectory (as you stated) then the above will never match and the directive does nothing.
That testing tool assumes the .htaccess file is located in the document root only. If your .htaccess was located in the document root and not the subdirectory, then that directive would indeed be OK.
In a directory context (eg. .htaccess) the RewriteRule pattern matches against the URL-path relative to the directory that contains the .htaccess file.
Aside:
In your link, the entire file would seem to be:
RewriteEngine On
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteCond %{REQUEST_FILENAME} !-l
#RewriteRule . index.php [L]
RewriteRule (\w+)/?$ test.php?user=$1 [L]
The first rule is commented out so does not apply here. However, if you uncomment that first rule then the rules are in the wrong order. Since a request for /prezzo/account/1 would first be rewritten to index.php and you'd have the same problem as before.
The order of rules is important.