How to use php to convert unicode and utf8?

How to use PHP to convert unicode and utf8: First, there is no need to consider the [4-6] byte encoding; then [utf-8] characters with more than four bytes appear, which can be directly regarded as garbled characters. Just ignore it or convert it to unicode entity form, the code is [$utf8char = "{$c};"].

How to use php to convert unicode and utf8:

Unicode encoding is to implement utf-8 and gb series The basis for encoding (gb2312, gbk, gb18030) conversion. Although we can also directly make a comparison table from utf-8 to these encodings, few people will do this because the variable encoding of utf-8 is uncertain. Therefore, in general, the comparison table between unicode and gb encoding is used. Unicode (UCS-2) is actually the basic encoding of utf-8, and utf-8 is just an implementation of it. The two have the following correspondence:

• Unicode symbol range | UTF-8 encoding method

• ##u0000 0000 - u0000 007F | 0xxxxxxx

• u0000 0080 - u0000 07FF | 110xxxxx 10xxxxxx

##u0000 0800 - u0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
Due to the characters currently used by utf-8 They are all in UCS-2, so there is no need to consider the 4-6 byte encoding. Similarly, during reverse conversion, if more than four bytes of UTF-8 characters appear, they can be directly regarded as garbled characters. Ignore or convert to unicode entity form ("long int;" form), and then hand it over to the browser or related parsing program for processing. The algorithm for converting unicode to utf-8 encoding using PHP is as follows:

/*
 * 参数 $c 是unicode字符编码的int类型数值，如果是用二进制读取的数据，在php中通常要用 hexdec(bin2hex( $bin_unichar )) 这样转换
 */
function uni2utf8( $c )
{
  if ($c < 0x80)
  {
        $utf8char = chr($c);
  }
  else if ($c < 0x800)
  {
        $utf8char = chr(0xC0 | $c >> 0x06).chr(0x80 | $c & 0x3F);
  }
  else if ($c < 0x10000)
  {
        $utf8char = chr(0xE0 | $c >> 0x0C).chr(0x80 | $c >> 0x06 & 0x3F).chr(0x80 | $c & 0x3F);
  }
  //因为UCS-2只有两字节，所以后面的情况是不可能出现的，这里只是说明unicode HTML实体编码的用法。
  else
  {
        $utf8char = "&#{$c};";
  }
  return $utf8char;
}

Within the current environment, it can be considered that utf-8 character set == unicode (UCS-2), but in theory, the inclusion relationship of the main character set relationships is as follows:

utf-8 > unicode(UCS-2) > gb18030 > gbk > gb2312

Therefore, if encoding When all are correct:

gb2312 => gbk => gb18030 => unicode(UCS-2) => utf-8

Such a transformation process is basically lossless, but on the contrary, by

utf-8 => unicode(UCS-2) => gb18030=> gbk => gb2312

In such a conversion process, it is very likely that there will be unrecognizable characters. Therefore, if the system uses UTF-8 encoding, try not to reverse the encoding operation easily.

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