Summary of mysql php garbled problem

Solve the problem of mysql php garbled characters: 1. Specify the character set of the database table when creating the database table; 2. Set the character set of mysql; 3. After connecting to the database, set the default character encoding used when transmitting characters between databases ;4. Set the character set used by the html page.

When php reads mysql, the following places involve the character set.

1. Specify the character set of the database table when creating the database table. For example

 create table tablename 
 ( 
 id int not null auto_increment, 
 title varchar(20) not null,  
 primary key ('id') 
 )DEFAULT CHARSET =UTF8;

If the character set of the table is not specified when creating the table, the default character set of the database to which the table belongs is used. The character set is specified by character_set_database.
The method to check the character set used by the database table is:

show create table mytable;

(PS: When establishing a database/table and performing database operations, try to explicitly indicate the character set used instead of relying on MySQL's default settings, otherwise MySQL may cause great trouble when upgrading [1])

2. Mysql character set
There are three important variables in mysql, character_set_client, character_set_results, and character_set_connection.
By setting character_set_client, tell Mysql what encoding method PHP stores in the database.
By setting character_set_results, tell Mysql what kind of encoded data PHP needs to get.
By setting character_set_connection, tell Mysql what encoding to use for the text in the PHP query.

3. After connecting to the database, set the default character encoding used when transmitting characters between databases.
Use mysqli::set_charset() or mysqli::query('set names utf8') to set.
Try to use mysqli::set_charset(mysqli:set_charset) instead of "SET NAMES" (refer to this article)

$db = new mysqli('localhost','user','passwd','database_name');$db->set_charset('utf8');

Note that it is utf8, not utf-8
(There is a problem here. , the database and PHP have unified the encoding, but if the mysqli::set_charset() function is not called, garbled characters will still appear when reading the data. Why is this?)
(In addition, set names utf8 is equivalent to the following three Sentence
SET character_set_client = utf8;
SET character_set_results = utf8;
SET character_set_connection = utf8;
)

4. The character set used by the html page. Set

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5 in the meta tag. The character set used by the php text file.
You can use vim to open the file under Linux, enter
:set encoding
to view the character set used by the file

To ensure that there is no garbled code, you need to ensure that the file itself is encoded, HTML The encoding specified in PHP tells Mysql to unify the encoding (including character_set_client and character_set_results). Also use the mysqli:set_charset() function or "SET NAMES".

In response to the question after "3", I wrote several examples to test the results of setting and not setting the character set after linking to the database. Test environment Ubuntu 12.04, MySQL 5.5, php 5.5.7.
The results are as follows:
(1) The character set of the database table is utf8. Without using set names utf8
can insert and read Chinese normally, but garbled characters are displayed in mysql

(2) The character set of the database table is utf8. Use set names utf8
to insert and read Chinese normally, and the display in mysql is correct

(3) The character set of the database table is not utf8. Use set names utf8
mysql In the display, the readings are all question marks.

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