What should I do if the Chinese characters displayed in Oracle in PHP are question marks?

When using PHP to connect to the Oracle database, sometimes the Chinese characters queried will display question marks. This is because the default character set of the Oracle database is the American ACSII character set and does not support the Chinese character set. In Oracle, if we need to support the Chinese character set, we need to set the character set of the Oracle database to the UTF-8 character set.

In order to solve the problem of Chinese characters being displayed as question marks, we need to first check whether the character set of the Oracle database is UTF-8 character set. It can be queried through the following SQL statement:

SELECT * FROM nls_database_parameters WHERE parameter LIKE '%CHARACTERSET';

If the queried character set is not the UTF-8 character set, then we need to set the character set of the Oracle database to the UTF-8 character set.

First of all, in the Oracle database, four character sets need to be set: database character set, database NCHAR character set, session character set and session NCHAR character set.

The database character set refers to the character set of non-Unicode character data in the database. The database NCHAR character set refers to the character set of Unicode character data in the database; the session character set refers to the characters used by the client when accessing the Oracle database. Set, session NCHAR character set refers to the Unicode character set used by the client when accessing the Oracle database.

To set the character set of the Oracle database to the UTF-8 character set, you first need to determine whether the system default character set is the UTF-8 character set. You can query it through the following command:

locale -a

If the UTF-8 character set is not queried, you can install it through the following command:

sudo apt-get install language-pack-zh-hans

After the installation is completed, you can check whether the installation is successful through the following command:

locale -a | grep zh_CN.utf8

Next, we can set the character set of the Oracle database. Assuming that our Oracle database SID is ORCL, then we can set it through the following command:

sqlplus / as sysdba
alter system enable restricted session;
alter system set job_queue_processes=0;
alter system set aq_tm_processes=0;
shutdown immediate;
startup mount;
alter system enable restricted session;
alter database open;
ALTER DATABASE CHARACTER SET INTERNAL_USE UTF8;
shutdown immediate;
startup mount;
alter system enable restricted session;
alter database open;
exit;

This command sets the character set of the Oracle database to the UTF-8 character set and restarts the Oracle service. After the setting is completed, we can query through php, and the Chinese characters queried will no longer display question marks.

However, it should be noted that when setting the character set, the database needs to be backed up to avoid data loss. In addition, the character set setting of the Oracle database needs to be operated with caution. Improper operation may cause the Oracle database to not operate normally. Therefore, when setting the character set, it is recommended to consult professionals to ensure the correctness and safety of the operation.

In short, by setting the character set of the Oracle database, the problem of Chinese characters being displayed as question marks can be solved, allowing us to better use the Chinese character set when using PHP to connect to the Oracle database.

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