Unicode代理对

echo chr(0x30) . chr(0x6f) . chr(0x30) . chr(0xfc);

$callback = function($match) { 
    return chr(hexdec($match[1])) . chr(hexdec($match[2]));
}
preg_replace_callback('#\\u([0-9a-f]{2})([0-9a-f]{2})#', $callback, $string);

$callback = create_function('$match', 
    'return chr(hexdec($match[1])) . chr(hexdec($match[2]));'
);
preg_replace_callback('#\\u([0-9a-f]{2})([0-9a-f]{2})#', $callback, $string);