PHP:检查字符串是 utf-8 还是 utf-16le

Question

我正在编写默认情况下以 utf-8 返回文档的函数，如果您提供特殊参数，它将返回 utf-16le 格式的内容。我开始为这个函数编写单元测试，我不明白的是如何检查编码是"utf-8"还是"utf-16le"。我已经尝试过mb_detect_encoding但即使在以下代码片段中，它也返回false：

$utf16Doc = mb_convert_encoding($doc, "utf-16le", "utf8");
$test = mb_detect_encoding($utf16Doc, "utf-16le");
var_dump($test);

欣赏任何想法，如何检查编码是utf-16le而不是utf-8。

Answer 1

一种通过 BOM 检测文件的 UTF-8/16/32 的简单方法(不适用于没有 BOM 的字符串或文件)

<?php
// Unicode BOM is U+FEFF, but after encoded, it will look like this.
define ('UTF32_BIG_ENDIAN_BOM'   , chr(0x00) . chr(0x00) . chr(0xFE) . chr(0xFF));
define ('UTF32_LITTLE_ENDIAN_BOM', chr(0xFF) . chr(0xFE) . chr(0x00) . chr(0x00));
define ('UTF16_BIG_ENDIAN_BOM'   , chr(0xFE) . chr(0xFF));
define ('UTF16_LITTLE_ENDIAN_BOM', chr(0xFF) . chr(0xFE));
define ('UTF8_BOM'               , chr(0xEF) . chr(0xBB) . chr(0xBF));
function detect_utf_encoding($filename) {
$text = file_get_contents($filename);
$first2 = substr($text, 0, 2);
$first3 = substr($text, 0, 3);
$first4 = substr($text, 0, 3);
if ($first3 == UTF8_BOM) return 'UTF-8';
elseif ($first4 == UTF32_BIG_ENDIAN_BOM) return 'UTF-32BE';
elseif ($first4 == UTF32_LITTLE_ENDIAN_BOM) return 'UTF-32LE';
elseif ($first2 == UTF16_BIG_ENDIAN_BOM) return 'UTF-16BE';
elseif ($first2 == UTF16_LITTLE_ENDIAN_BOM) return 'UTF-16LE';
}
?>

所以现在你可以这样尝试，

$utf16Doc = mb_convert_encoding($doc, "utf-16le", "utf8");
$test = detect_utf_encoding($utf16Doc);
var_dump($test);

明确声明：这不是我自己的书面回答。我刚刚在 php.net 官方网站上找到了它，由用户 http://php.net/manual/en/function.mb-detect-encoding.php#68607mb_detect_encoding.希望这会以某种方式帮助您