确保 PHP 中的有效 UTF-8

问题描述

我使用 PHP 来处理来自各种来源的文本.我不认为它会是 UTF-8 以外的任何东西，ISO 8859-1 或 Windows-1252.如果不是其中之一，我只需要确保文本变成有效的 UTF-8 字符串，即使字符丢失.iconv 的//TRANSLIT 选项可以解决这个问题吗?

I'm using PHP to handle text from a variety of sources. I don't anticipate it will be anything other than UTF-8, ISO 8859-1, or perhaps Windows-1252. If it's anything other than one of those, I just need to make sure the text gets turned into a valid UTF-8 string, even if characters are lost. Does the //TRANSLIT option of iconv solve this?

例如，此代码能否确保将字符串安全地插入到 UTF-8 编码的文档(或数据库)中?

For example, would this code ensure that a string is safe to insert into a UTF-8 encoded document (or database)?

function make_safe_for_utf8_use($string) {

    $encoding = mb_detect_encoding($string, "UTF-8,ISO-8859-1,WINDOWS-1252");

    if ($encoding != 'UTF-8') {
        return iconv($encoding, 'UTF-8//TRANSLIT', $string);
    }
    else {
        return $string;
    }
}

推荐答案

UTF-8 可以存储任何 Unicode 字符.如果您的编码完全不同，包括 ISO-8859-1 或 Windows-1252，则 UTF-8 可以存储其中的每个字符.因此，当您将字符串从任何其他编码转换为 UTF-8 时，您不必担心丢失任何字符.

UTF-8 can store any Unicode character. If your encoding is anything else at all, including ISO-8859-1 or Windows-1252, UTF-8 can store every character in it. So you don't have to worry about losing any characters when you convert a string from any other encoding to UTF-8.

此外，ISO-8859-1 和 Windows-1252 都是单字节编码，其中任何字节都是有效的.在技​​术上无法区分它们.我会选择 Windows-1252 作为非 UTF-8 序列的默认匹配，因为唯一解码不同的字节是范围 0x80-0x9F.这些解码为各种字符，如 Windows-1252 中的智能引号和欧元，而在 ISO-8859-1 中，它们是几乎从未使用过的不可见控制字符.网络浏览器有时可能会说他们使用的是 ISO-8859-1，但通常他们真的会使用 Windows-1252.

Further, both ISO-8859-1 and Windows-1252 are single-byte encodings where any byte is valid. It is not technically possible to distinguish between them. I would chose Windows-1252 as your default match for non-UTF-8 sequences, as the only bytes that decode differently are the range 0x80-0x9F. These decode to various characters like smart quotes and the Euro in Windows-1252, whereas in ISO-8859-1 they are invisible control characters which are almost never used. Web browsers may sometimes say they are using ISO-8859-1, but often they will really be using Windows-1252.

此代码是否可以确保将字符串安全地插入到 UTF-8 编码的文档中

would this code ensure that a string is safe to insert into a UTF-8 encoded document

为此，您当然希望将可选的strict"参数设置为 TRUE.但我不确定这是否真的涵盖了所有无效的 UTF-8 序列.该函数不要求明确检查字节序列的 UTF-8 有效性.已知有 mb_detect_encoding 之前会错误地猜测 UTF-8 的情况，但我不知道在严格模式下是否仍然会发生这种情况.

You would certainly want to set the optional ‘strict’ parameter to TRUE for this purpose. But I'm not sure this actually covers all invalid UTF-8 sequences. The function does not claim to check a byte sequence for UTF-8 validity explicitly. There have been known cases where mb_detect_encoding would guess UTF-8 incorrectly before, though I don't know if that can still happen in strict mode.

如果您想确定，请使用 W3 推荐的正则表达式:

If you want to be sure, do it yourself using the W3-recommended regex:

if (preg_match('%^(?:
      [x09x0Ax0Dx20-x7E]            # ASCII
    | [xC2-xDF][x80-xBF]             # non-overlong 2-byte
    | xE0[xA0-xBF][x80-xBF]         # excluding overlongs
    | [xE1-xECxEExEF][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))
    return $string;
else
    return iconv('CP1252', 'UTF-8', $string);

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