How to create database connection in CodeIgniter framework

How to create a database connection in the CodeIgniter framework

Introduction:
CodeIgniter is a popular PHP development framework. It provides a set of simple and powerful tools to help developers quickly build efficient Web application. In CodeIgniter, the database is a key component, so it is very important to understand how to create and use database connections in the framework.

Step 1: Configure database settings
In CodeIgniter, we first need to configure database settings. Open the database.php file in the application/config directory and set the relevant parameters of the database, including database type, host, user name, password, and database name. The following is a simple example configuration:

$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => 'root',
    'database' => 'mydatabase',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
);

Step 2: Load the database class library
Before using the database, we need to load the database class library provided by the CodeIgniter framework. In a controller or model that needs to use a database, use the following code to load the database class library:

$this->load->database();

The above code will automatically load and initialize the database class library, using the default database settings in the configuration file.

Step 3: Create a database connection object
In CodeIgniter, we can create a database connection object by calling the method of the database class library. Here are some common method examples:

1. Query data:

   $query = $this->db->query("SELECT * FROM tableName");

2. Insert data:

   $data = array(
    'columnName' => 'value',
    'columnName2' => 'value2'
   );
   
   $this->db->insert('tableName', $data);

3. Update data:

   $data = array(
    'columnName' => 'value',
    'columnName2' => 'value2'
   );
   
   $this->db->where('columnName', $value);
   $this->db->update('tableName', $data);

4. Delete data:

   $this->db->where('columnName', $value);
   $this->db->delete('tableName');

It should be noted that the above examples are for reference only, and the specific operation method is based on Make adjustments according to actual conditions.

Step 4: Process the database query results
In CodeIgniter, we can process the database query results through the following methods:

1. Get a single row of data:

   $row = $query->row();

2. Get multiple rows of data:

   $result = $query->result();

3. Get the value of a specific field:

   $value = $row->columnName;

4. Get query results Number of rows:

   $numRows = $query->num_rows();

The above are just some basic examples, the CodeIgniter framework also provides many other methods that can be used to process query results.

Summary:
Creating and using database connections in the CodeIgniter framework is very simple. By configuring the database settings, loading the database class library, and calling the appropriate methods, we can easily perform database addition, deletion, modification, and query operations. At the same time, CodeIgniter also provides a wealth of query result processing methods to facilitate us to further process and operate the data. The above is a simple guide that I hope will be helpful to beginners.

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