PHP reads mysql garbled code and shares the principle of solving it with set names XXX

Let’s talk about MySQL’s character set first. Under Windows, you can copy the code

by modifying the

PHP code in my.ini. The code is as follows:

[mysql]
default-character-set=utf8 //The default character set of the client
[mysqld]
default-character-set=utf8 //The default character set on the server side

Suppose we set both to utf8, and then enter "show variebles like "character_set_%";" in the MySQL Command Line Client, you can see The following characters:

Copy code The code is as follows:

character_set_client latin1
character_set_connection latin1
character_set_database utf8
character_set_results latin1
character_set_server utf8
character _set_system utf8

If we use UTF-8 PHP program from the database When reading data, it is likely to be a string of "?????" or other garbled characters.
The solution is to execute a query "SET NAMES UTF8" after connecting to the database and before reading the data, which is
mysql_query("SET NAMES UTF8");
//This sentence must be placed in PHP After the database server connection statement [$c die("Connection to server failed");], the display will be normal (as long as the characters of the information in the database are normal).
Go to the MySQL command line and enter "SET NAMES UTF8;", then execute "show variebles like "character_set_%";" and find that the values ​​of the variables "character_set_client", "character_set_connection" and "character_set_results" that were originally latin1 have all changed to utf8 Well, it turns out that these three variables are causing trouble.
Check the manual, the above sentence is equivalent to:
SET character_set_client = utf8;
SET character_set_results = utf8;
SET character_set_connection = utf8;
Look at the functions of these three variables:
Information input path: client→connection→server;
Information Output path: server→connection→results.
In other words, each path needs to change the character set encoding 3 times. Take the garbled output as an example. For the utf8 data in the server, the incoming connection is converted to latin1, the incoming results are converted to latin1, and the utf-8 page converts the results again. If the two character sets are incompatible, such as latin1 and utf8, the conversion process is irreversible and destructive.
But it should be stated here that the effect of "SET NAMES UTF8" is only temporary, and MySQL will return to the default after restarting.
The next step is to talk about the configuration of MySQL on the server. Don't we have to add "SET NAMESUTF8" every time we read and write to the database to ensure that the encoding of data transmission is consistent? Can I configure MySQL so that those three variables default to the character set we want? The manual doesn't say it, and I couldn't find the answer online. Therefore, from a server configuration perspective, there is no way to omit that line of code.
Summary: In order to allow your webpage to be displayed normally on more servers, it is better to add "SET NAMES UTF8". Even if you do not add this sentence now, you can still access it normally.
The above has introduced the principle of using set names XXX to solve the problem of php reading mysql garbled code, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.