首先必须检测使用了什么编码。在解析RSS提要时(可能通过HTTP)，应该从Content-Type HTTP报头字段的字符集参数中读取编码。如果不存在，则从XML处理指令的encoding属性中读取编码。如果也没有，请使用规范中定义的UTF-8。

以下是我可能会做的:

I’d use cURL to send and fetch the response. That allows you to set specific header fields and fetch the response header as well. After fetching the response, you have to parse the HTTP response and split it into header and body. The header should then contain the Content-Type header field that contains the MIME type and (hopefully) the charset parameter with the encoding/charset too. If not, we’ll analyse the XML PI for the presence of the encoding attribute and get the encoding from there. If that’s also missing, the XML specs define to use UTF-8 as encoding.

$url = 'http://www.lr-online.de/storage/rss/rss/sport.xml';

$accept = array(
    'type' => array('application/rss+xml', 'application/xml', 'application/rdf+xml', 'text/xml'),
    'charset' => array_diff(mb_list_encodings(), array('pass', 'auto', 'wchar', 'byte2be', 'byte2le', 'byte4be', 'byte4le', 'BASE64', 'UUENCODE', 'HTML-ENTITIES', 'Quoted-Printable', '7bit', '8bit'))
);
$header = array(
    'Accept: '.implode(', ', $accept['type']),
    'Accept-Charset: '.implode(', ', $accept['charset']),
);
$encoding = null;
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_HTTPHEADER, $header);
$response = curl_exec($curl);
if (!$response) {
    // error fetching the response
} else {
    $offset = strpos($response, "\r\n\r\n");
    $header = substr($response, 0, $offset);
    if (!$header || !preg_match('/^Content-Type:\s+([^;]+)(?:;\s*charset=(.*))?/im', $header, $match)) {
        // error parsing the response
    } else {
        if (!in_array(strtolower($match[1]), array_map('strtolower', $accept['type']))) {
            // type not accepted
        }
        $encoding = trim($match[2], '"\'');
    }
    if (!$encoding) {
        $body = substr($response, $offset + 4);
        if (preg_match('/^<\?xml\s+version=(?:"[^"]*"|\'[^\']*\')\s+encoding=("[^"]*"|\'[^\']*\')/s', $body, $match)) {
            $encoding = trim($match[1], '"\'');
        }
    }
    if (!$encoding) {
        $encoding = 'utf-8';
    } else {
        if (!in_array($encoding, array_map('strtolower', $accept['charset']))) {
            // encoding not accepted
        }
        if ($encoding != 'utf-8') {
            $body = mb_convert_encoding($body, 'utf-8', $encoding);
        }
    }
    $simpleXML = simplexml_load_string($body, null, LIBXML_NOERROR);
    if (!$simpleXML) {
        // parse error
    } else {
        echo $simpleXML->asXML();
    }
}

整理完PHP脚本后，不要忘记告诉MySQL你要传递的字符集和你想要接收的字符集。

例如:设置为UTF-8

在Latin 1 I/O会话中将UTF-8数据传递给Latin 1表会导致这些讨厌的鸟脚。我每隔一天就会在OsCommerce商店看到这个。后面和第四个似乎是对的。但是phpMyAdmin会显示真相。通过告诉MySQL你正在传递什么字符集，它将为你处理MySQL数据的转换。

如何恢复现有的乱码MySQL数据是另一个问题。：）

关于mb_detect_encoding和mb_convert_encoding有趣的事情是，您建议的编码顺序确实很重要:

// $input is actually UTF-8

mb_detect_encoding($input, "UTF-8", "ISO-8859-9, UTF-8");
// ISO-8859-9 (WRONG!)

mb_detect_encoding($input, "UTF-8", "UTF-8, ISO-8859-9");
// UTF-8 (OK)

因此，在指定预期的编码时，您可能希望使用特定的顺序。不过，请记住，这并非万无一失。

一个实现isutf8函数的好方法可以在php.net上找到:

function isUTF8($string) {
    return (utf8_encode(utf8_decode($string)) == $string);
}

此版本适用于德语，但您可以修改$CHARSETS和$TESTCHARS。

class CharsetDetector
{
    private static $CHARSETS = array(
        "ISO_8859-1",
        "ISO_8859-15",
        "CP850"
    );

    private static $TESTCHARS = array(
        "€",
        "ä",
        "Ä",
        "ö",
        "Ö",
        "ü",
        "Ü",
        "ß"
    );

    public static function convert($string)
    {
        return self::__iconv($string, self::getCharset($string));
    }

    public static function getCharset($string)
    {
        $normalized = self::__normalize($string);
        if(!strlen($normalized))
            return "UTF-8";
        $best = "UTF-8";
        $charcountbest = 0;
        foreach (self::$CHARSETS as $charset)
        {
            $str = self::__iconv($normalized, $charset);
            $charcount = 0;
            $stop = mb_strlen($str, "UTF-8");

            for($idx = 0; $idx < $stop; $idx++)
            {
                $char = mb_substr($str, $idx, 1, "UTF-8");
                foreach (self::$TESTCHARS as $testchar)
                {
                    if($char == $testchar)
                    {
                        $charcount++;
                        break;
                    }
                }
            }

            if($charcount > $charcountbest)
            {
                $charcountbest = $charcount;
                $best = $charset;
            }
            //echo $text . "<br />";
        }
        return $best;
    }

    private static function __normalize($str)
    {
        $len = strlen($str);
        $ret = "";
        for($i = 0; $i < $len; $i++)
        {
            $c = ord($str[$i]);
            if ($c > 128) {
                if (($c > 247))
                    $ret .= $str[$i];
                elseif
                    ($c > 239) $bytes = 4;
                elseif
                    ($c > 223) $bytes = 3;
                elseif
                    ($c > 191) $bytes = 2;
                else
                    $ret .= $str[$i];

                if (($i + $bytes) > $len)
                    $ret .= $str[$i];
                $ret2 = $str[$i];
                while ($bytes > 1)
                {
                    $i++;
                    $b = ord($str[$i]);
                    if ($b < 128 || $b > 191)
                    {
                        $ret .= $ret2;
                        $ret2 = "";
                        $i += $bytes-1;
                        $bytes = 1;
                        break;
                    }
                    else
                        $ret2 .= $str[$i];
                    $bytes--;
                }
            }
        }
        return $ret;
    }

    private static function __iconv($string, $charset)
    {
        return iconv ($charset, "UTF-8", $string);
    }
}

当你试着掌握多种语言时，比如日语和韩语，你可能会遇到麻烦。

带有'auto'参数的Mb_convert_encoding不能很好地工作。设置mb_detect_order('ASCII,UTF-8,JIS,EUC- jp,SJIS,EUC- kr,UHC')没有帮助，因为它会错误地检测EUC-*。

我的结论是，只要输入字符串来自HTML，它就应该在元元素中使用“字符集”。我使用Simple HTML DOM Parser，因为它支持无效的HTML。

下面的代码片段从网页中提取title元素。如果您想转换整个页面，那么您可能需要删除一些行。

<?php
require_once 'simple_html_dom.php';

echo convert_title_to_utf8(file_get_contents($argv[1])), PHP_EOL;

function convert_title_to_utf8($contents)
{
    $dom = str_get_html($contents);
    $title = $dom->find('title', 0);
    if (empty($title)) {
        return null;
    }
    $title = $title->plaintext;
    $metas = $dom->find('meta');
    $charset = 'auto';
    foreach ($metas as $meta) {
        if (!empty($meta->charset)) { // HTML5
            $charset = $meta->charset;
        } else if (preg_match('@charset=(.+)@', $meta->content, $match)) {
            $charset = $match[1];
        }
    }
    if (!in_array(strtolower($charset), array_map('strtolower', mb_list_encodings()))) {
        $charset = 'auto';
    }
    return mb_convert_encoding($title, 'UTF-8', $charset);
}