php - 有人可以解释这个正则表达式吗？

Question

/^[\p{Ll}\p{Lm}\p{Lo}\p{Lt}\p{Lu}\p{Nd}]+$/mu

这是 cakePHP 用来验证字母数字字符串的正则表达式验证。我无法理解 Ll、Lm、Lt 等是什么？这是为了验证字母数字字符串，因此他们应该测试数字和字符。谁能稍微解释一下这个表达式。

谢谢。

Answer 1

Ll、Lm、Lo、Lt、Lu、Nd 是 unicode 字符类。

在页面的大约 1/3 处查看此处:

http://www.regular-expressions.info/unicode.html

• \p{Ll} or \p{Lowercase_Letter}: a lowercase letter that has an uppercase variant.
• \p{Lu} or \p{Uppercase_Letter}: an uppercase letter that has a lowercase variant.
• \p{Lt} or \p{Titlecase_Letter}: a letter that appears at the start of a word when only the first letter of the word is capitalized.
• \p{L&} or \p{Letter&}: a letter that exists in lowercase and uppercase variants (combination of Ll, Lu and Lt).
• \p{Lm} or \p{Modifier_Letter}: a special character that is used like a letter.
• \p{Lo} or \p{Other_Letter}: a letter or ideograph that does not have lowercase and uppercase variants.