How to solve Chinese garbled query in MySQL database with PHP?

#How does PHP solve Chinese garbled characters when querying MySQL database?

1. The default encoding of the MySQL database is UTF-8;

2. When creating a table in MySQL, set the character set to UTF-8;

3. Before querying data in PHP, set the database encoding to UTF-8.

MySQL "SET NAMES x" character set problem analysis

I recently received training from BBT to build a voting system. The system code is not difficult, but my time was mainly spent studying character sets and encodings. The encoding (character set) issues of the MySQL and Apache systems made me rack my brains and suffer a lot. The solutions to these problems on the Internet are scattered and one-sided. Most of them provide solutions without explaining why. So I will summarize what I have gained in the past few days to avoid latecomers from taking detours again. This article is a little helpful for PHP writing (after reading it, you will know how to make your PHP program display normally on the servers of most space providers), but more help lies in the establishment and settings of the network server.

Let’s talk about MySQL’s character set first. Under Windows, you can change the default character set of the database by modifying the two fields

# CLIENT SECTION
[mysql]
default-character-set=utf8
# SERVER SECTION
[mysqld]
default-character-set=utf8

in my.ini. The first is the client's default character set, and the second is the server's default character set. 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:

character_set_client latin1
character_set_connection latin1
character_set_database utf8
character_set_results latin1
character_set_server utf8
character_set_system utf8

The utf8 follows our above Change the setting. At this time, if we read data from the database through a PHP program using UTF-8, it is likely to be a string of "?????" or other garbled characters. After searching online for a long time, the solution is simple. After connecting to the database, before reading the data, first execute a query "SET NAMES UTF8", that is,

mysql_query("SET NAMES UTF8");

in PHP, and the display will be normal (as long as the database The characters in the information are normal). Why is this happening? What exactly does the query "SET NAMES UTF8" do?

Go to the MySQL command line and enter "SET NAMES UTF8;", then execute "show variebles like "character_set_%";" and find that the variables "character_set_client", "character_set_connection" and "character_set_results" that were originally latin1 All the values ​​have changed to utf8. It turns out that these three variables are causing trouble. Consult the manual, the above sentence is equal 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. So it can't be turned back.

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.

Next, let’s talk about the configuration of MySQL on the server. Don't we have to add "SET NAMES UTF8" 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.

Recommended tutorials: "PHP" "MySQL Tutorial"

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