如何反转Unicode字符串

这是使用正则表达式的另一种方法:

function utf8_strrev($str){
 preg_match_all('/./us', $str, $ar);
 return implode(array_reverse($ar[0]));
}

这是另一种方式.这似乎工作,而无需指定输出编码(使用几个不同的mb_internal_encodings 测试):

function mb_strrev($text)
{
    return join('', array_reverse(
        preg_split('~~u', $text, -1, PREG_SPLIT_NO_EMPTY)
    ));
}

字形函数比mbstring和PCRE函数更正确地处理UTF-8字符串/ Mbstring和PCRE可能会破坏字符。通过执行以下代码，您可以看到它们之间的差异。

function str_to_array($string)
{
    $length = grapheme_strlen($string);
    $ret = [];

    for ($i = 0; $i < $length; $i += 1) {

        $ret[] = grapheme_substr($string, $i, 1);
    }

    return $ret;
}

function str_to_array2($string)
{
    $length = mb_strlen($string, "UTF-8");
    $ret = [];

    for ($i = 0; $i < $length; $i += 1) {

    $ret[] = mb_substr($string, $i, 1, "UTF-8");
}

    return $ret;
}

function str_to_array3($string)
{
    return preg_split('//u', $string, -1, PREG_SPLIT_NO_EMPTY);
}

function utf8_strrev($string)
{
    return implode(array_reverse(str_to_array($string)));
}

function utf8_strrev2($string)
{
    return implode(array_reverse(str_to_array2($string)));
}

function utf8_strrev3($string)
{
    return implode(array_reverse(str_to_array3($string)));
}

// http://www.php.net/manual/en/function.grapheme-strlen.php
$string = "a\xCC\x8A"  // 'LATIN SMALL LETTER A WITH RING ABOVE' (U+00E5)
         ."o\xCC\x88"; // 'LATIN SMALL LETTER O WITH DIAERESIS'  (U+00F6)

var_dump(array_map(function($elem) { return strtoupper(bin2hex($elem)); },
[
  'should be' => "o\xCC\x88"."a\xCC\x8A",
  'grapheme' => utf8_strrev($string),
  'mbstring' => utf8_strrev2($string),
  'pcre' => utf8_strrev3($string)
]));

结果在这里。

array(4) {
  ["should be"]=>
  string(12) "6FCC8861CC8A"
  ["grapheme"]=>
  string(12) "6FCC8861CC8A"
  ["mbstring"]=>
  string(12) "CC886FCC8A61"
  ["pcre"]=>
  string(12) "CC886FCC8A61"
}

从PHP 5.5（intl 3.0）开始可以使用IntlBreakIterator;

function utf8_strrev($str)
{
    $it = IntlBreakIterator::createCodePointInstance();
    $it->setText($str);

    $ret = '';
    $pos = 0;
    $prev = 0;

    foreach ($it as $pos) {
        $ret = substr($str, $prev, $pos - $prev) . $ret;
        $prev = $pos;
    }

    return $ret;  
}