PHP正则表达式缺少捕获组

Question

I'm trying to parse several coordinates, but PHP preg_match is missing a capture group. It works in every regex simulator I've tested, but not in my code. Group 4 always comes up empty;

$coordinates = 'N40.765775°  E8.303369°';
// -40.765775°  -8.303369°
//  40.765775°  8.303369°
// -40.765775°  8.303369°
// N40.765775°  E8.303369°
// S40.765775°  E8.303369°
// N40.765775°  W8.303369°
// S40.765775°  W8.303369°

$regex = '/([-NnSs]?)\D*([0-9]?[0-9])\.(\d{1,10}+)\D\h*([-EeWw]?)\D*([0-1]?[0-9]?[0-9])\.(\d{1,10}+)/';
if (preg_match($regex, $coordinates, $matches)) {
    print_r($matches);
} else {
    echo "no matches";
}

Answer 1

Since you are parsing strings that have multibyte characters (°), you should add the unicode modifier, i.e. u at the end of the regex.

/      /u

Just as an illustration: without that modifier, if you would add a . after \D, here:

\D.\h*([-EeWw]?)

... then you would capture the "E" in the fourth capture group. So \D. actually matches the multibyte character °.