Re-understand unicode and utf8 encoding

Re-recognize unicode and utf8 encoding

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Until today, just now to be precise, I didn’t know that UTF-8 encoding and Unicode encoding are different, there is a difference囧
There is a certain connection between them Yes, look at their differences:

<code>UTF-8的长度是不一定的，有可能是1、2、3字节
Unicode长度一定，2个字节（USC-2）
UTF-8可以和Unicode互相转换</code>

The relationship between unicode and utf8

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Unicode (16)	UTF-8 (binary)
0000 - 007F	0xxxxxxx
0080 - 07FF	110xxxxx 10xxxxxx
0800 - FFFF	1110xxxx 10xxxxxx 10xxxxxx

The above table has two meanings. The first one is obviously Unicode Correspondence to UTF-8 character range , there is another way to see how Unicode and UTF-8 can be converted to each other:

Let’s talk about the conversion from UTF-8 to Unicode first

UTF-8 encoded binary is matched with the above three formats, and the fixed bits are removed after matching (Non-x position in the table), and then every 8-bit group from right to left. If there are not enough 8-bits, the left side will not be collected. Make up 2 bytes and 16 bits. These 16 bits represent the Unicode encoding corresponding to UTF-8. , take a look at the following examples:

The text encoding format in the above picture is UTF-8, and you can use WinHex to see its hexadecimal representation

<code>字符	=> UTF-8	  => UTF-8二进制=> 去掉固定位置凑够16位的二进制 => 16进制

汉 	=> E6B189 => 11100110 10110001 10001001	=> 01101100 01001001 => 6C49
汉 	=> E5AD97 => 11100101 10101101 10010111	=> 01011011	01010111 => 5B57

#下面是在chrome命令行下面运行的结果
'\u6C49'
"汉"
'\u5B57'
"字"

#到这里的话，从UTF-8转换到Unicode已经是一件非常容易的事了，看看转换的伪代码
读取一个字节，11100110
判断该UTF-8字符的格式，属于第三种，3个字节
继续读取2个字节得到 11100101 10101101 10010111
按照格式去掉固定位     1011011 01010111
不够16位，左边补零    01011011 01010111  => 5B57</code>

Let’s look at the conversion from Unicode to UTF-8

<code>5B57
获取5B57所在的Unicode范围，0800 </code>

Let’s talk about the problem

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Let’s talk about the cause of today’s problem. Many words are input from the front end. Each word in UTF-8 format has a maximum of 30 bytes, so verification will be done on the front end and backend respectively. JavaScript uses Unicode encoding. The back-end program uses UTF-8 encoding, and the current solution is as follows

Front-end

<code>function utf8_bytes(str)
{
	var len = 0, unicode;
	for(var i = 0; i </code>

Backend

<code>#对于GBK字符串
$len = ceil(strlen(bin2hex(iconv('GBK', 'UTF-8', $word)))/2);
#对于UTF8字符串
$len = ceil(strlen(bin2hex($word))/2);</code>

5/21/2015 8:21:53 PM

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The above has introduced the re-understanding of unicode and utf8 encoding, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.