Description:
------------
The manual section "Character classes" of the PCRE documentation contains a quote from the original PCRE documentation: "In UTF-8 mode, characters with values greater than 128 do not match any of the POSIX character classes."

While for the original PCRE library this is true, it is, however, untrue concerning the PCRE implementation for PHP. The `u` modifier in PHP actually means PCRE_UTF8 | PCRE_UCP; the latter making character classes like [[:digit:]] also match e.g. Persian digits. Which certainly are above code-point 128.

This misleading quote should be removed from the manual and possibly be substituted for a note/warning that, when using the `u` modifier, character classes are changed. From the original PCRE docs (http://www.pcre.org/original/doc/html/pcrepattern.html#SEC10):

However, if the PCRE_UCP option is passed to pcre_compile(), some of the classes are changed so that Unicode character properties are used. This is achieved by replacing certain POSIX classes by other sequences, as follows:

  [:alnum:]  becomes  \p{Xan}
  [:alpha:]  becomes  \p{L}
  [:blank:]  becomes  \h
  [:digit:]  becomes  \p{Nd}
  [:lower:]  becomes  \p{Ll}
  [:space:]  becomes  \p{Xps}
  [:upper:]  becomes  \p{Lu}
  [:word:]   becomes  \p{Xwd}

A little more context and the answer inspiring this bug-report on Stackoverflow: http://stackoverflow.com/q/37658139/255756

Test script:
---------------
$string = 'I have ۳ apples and 5 oranges.';

preg_match_all('/\d+/u', $string, $m);
var_export($m);


Expected result:
----------------
// According to the docs, this should be dumped

array (
  0 => 
  array (
    0 => '5',
  ),
)

Actual result:
--------------
array (
  0 => 
  array (
    0 => '۳',
    1 => '5',
  ),
)