Question

^(?![_\.\'\-])(?:[\p{L} ]+)$

If I understand correctly, there is:

• (?![_\.\'\-]) a negative lookahead, that is the string cannot start with underscore, point, apostrophe or minus sign (any number of).
• (?:[\p{L} ]+) allowing at least one character in Ll, Lm, Lo, Lt and Lu and spaces.

First question is: something like “1Bob” should not fail (because of the lookahead). So why it fails?

Second question is where I can find a list or explanation of characters in Ll, Lm, Lo, Lt and Lu?

Answer 1

The digit "1" is not matched by \p{L} (this matches only letters!). If you want to match any (numeric) digit, use the class \p{N} as well:

$text = "1Bob";

if (preg_match("/^(?![_\.\'\-])(?:[\p{N}\p{L} ]+)$/u", $text)) {
  echo "Matched!\n";
} else {
  echo "No match...\n";
}

which will print:

Matched!

Also, there are small differences between Ruby’s regex engine and that of PHP. Since your target language seems to be PHP, I recommend testing it with PHP, not with Rubular (Ruby).

Note that inside character classes, the “normal” regex meta chars don’t have any special powers and need not be escaped: preg_match("/^(?![_.'-])(?:[\p{N}\p{L} ]+)$/u", $text)

An overview of many Unicode Character Properties/Classes can be found here: http://www.regular-expressions.info/unicode.html