PHP正则表达式值

Question

My Regexp:

/^(\p{L}+)(?:\.(\p{L}+))*$/

and subject:

app.config.db

It returns matches app and db . Why this script omit config ?

Answer 1

Because of this part:

(?:\.(\p{L}+))*

You're repeating a capturing group, which will only ever capture the last capture. You might want to look into preg_match_all() , which (with a different regex) would be able to return all of the matches.

Example:

$input = 'app.config.db';
$regex = '/\.?(\p{L}+)/';

preg_match_all($regex, $input, $matches);
print_r($matches[1]);

Output:

Array
    (
        [0] => app
        [1] => config
        [2] => db
    )

Answer 2

Your regex contains two capturing groups, so it will capture two strings. The first group ( ^(\\p{L}+) ) captures app because it's at the beginning of the string.

The second group initially captures config . But it's nested inside a * , so it repeats and captures db . In general, the result will be the last string captured by any group.