这个备备单列出了PHP中与UTF-8处理相关的一些常见注意事项: http://developer.loftdigital.com/blog/php-utf-8-cheatsheet

这个函数在字符串中检测多字节字符也可能是有帮助的(来源):

function detectUTF8($string) { return preg_match('%(?: [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte |\xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs |[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte |\xED[\x80-\x9F][\x80-\xBF] # excluding surrogates |\xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3 |[\xF1-\xF3][\x80-\xBF]{3} # planes 4-15 |\xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16 )+%xs', $string); }

这很简单:当您得到一些不是UTF-8的东西时，您必须将其编码为UTF-8。

因此，当你获取某个ISO 8859-1的提要时，通过utf8_encode解析它。

但是，如果您正在获取UTF-8提要，则不需要做任何事情。

检测编码是困难的。

mb_detect_encoding works by guessing, based on a number of candidates that you pass it. In some encodings, certain byte-sequences are invalid, an therefore it can distinguish between various candidates. Unfortunately, there are a lot of encodings, where the same bytes are valid (but different). In these cases, there is no way to determine the encoding; You can implement your own logic to make guesses in these cases. For example, data coming from a Japanese site might be more likely to have a Japanese encoding.

As long as you only deal with Western European languages, the three major encodings to consider are utf-8, iso-8859-1 and cp-1252. Since these are defaults for many platforms, they are also the most likely to be reported wrongly about. Eg. if people use different encodings, they are likely to be frank about it, since else their software would break very often. Therefore, a good strategy is to trust the provider, unless the encoding is reported as one of those three. You should still doublecheck that it is indeed valid, using mb_check_encoding (note that valid is not the same as being - the same input may be valid for many encodings). If it is one of those, you can then use mb_detect_encoding to distinguish between them. Luckily that is fairly deterministic; You just need to use the proper detect-sequence, which is UTF-8,ISO-8859-1,WINDOWS-1252.

一旦检测到编码，就需要将其转换为内部表示(UTF-8是唯一明智的选择)。函数utf8_encode将ISO-8859-1转换为UTF-8，因此它只能用于特定的输入类型。对于其他编码，使用mb_convert_encoding。

if(!mb_check_encoding($str)){
    $str = iconv("windows-1251", "UTF-8", $str);
}

这对我很有帮助

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();
    }
}

我在http://deer.org.ua/2009/10/06/1/:上找到了一个解决方案

class Encoding
{
    /**
     * http://deer.org.ua/2009/10/06/1/
     * @param $string
     * @return null
     */
    public static function detect_encoding($string)
    {
        static $list = ['utf-8', 'windows-1251'];

        foreach ($list as $item) {
            try {
                $sample = iconv($item, $item, $string);
            } catch (\Exception $e) {
                continue;
            }
            if (md5($sample) == md5($string)) {
                return $item;
            }
        }
        return null;
    }
}

$content = file_get_contents($file['tmp_name']);
$encoding = Encoding::detect_encoding($content);
if ($encoding != 'utf-8') {
    $result = iconv($encoding, 'utf-8', $content);
} else {
    $result = $content;
}

我认为@是一个糟糕的决定，并对deer.org.ua的解决方案做了一些更改。