Introduction to using the database class that comes with CodeIgniter_PHP tutorial

In CodeIgniter, using the database is very frequent. You can use the database class that comes with the framework to perform database operations conveniently.

Initialize database class

Load and initialize the database class according to your database configuration:

$this->load->database();

Once loaded you can use it anywhere.

Return query results in object form

$query = $this->db->query('SELECT name, title, email FROM my_table');

foreach ($query->result() as $row)
{
    echo $row->title;
    echo $row->name;
    echo $row->email;
}

echo 'Total Results: ' . $query->num_rows();

The result() function above returns an array of objects. For example: $row->title

Return query results in the form of array

$query = $this->db->query('SELECT name, title, email FROM my_table');

foreach ($query->result_array() as $row)
{
    echo $row['title'];
    echo $row['name'];
    echo $row['email'];
}

The result_array() function above returns an array with subscripts. For example: $row['title']

Return a piece of data

Object form:

$query = $this->db->query('SELECT name FROM my_table LIMIT 1');

$row = $query->row();
echo $row->name;

The row() function above returns an object. For example: $row->name

Array format:

$query = $this->db->query('SELECT name FROM my_table LIMIT 1');

$row = $query->row_array();
echo $row['name'];

The row_array() function above returns an array. For example: $row['name']

Insert data

$sql = "INSERT INTO mytable (title, name) 
        VALUES (".$this->db->escape($title).", ".$this->db->escape($name).")";

$this->db->query($sql);

echo $this->db->affected_rows();

Quick insertion method:

$data = array(
               'title' => $title,
               'name' => $name,
               'date' => $date
            );

$this->db->insert('mytable', $data); 

// Produces: INSERT INTO mytable (title, name, date) VALUES ('{$title}', '{$name}', '{$date}')

Database configuration

CodeIgniter has a configuration file that allows you to store database connection values ​​(username: user name, password: password, database name: database name, etc...). The configuration file is located in the following path: application/config/database.php

Accessory files are stored in a multi-dimensional array in the following format:

$db['default']['hostname'] = "localhost";
$db['default']['username'] = "root";
$db['default']['password'] = "";
$db['default']['database'] = "database_name";
$db['default']['dbdriver'] = "mysql";
$db['default']['dbprefix'] = "";
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = FALSE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = "";
$db['default']['char_set'] = "utf8";
$db['default']['dbcollat'] = "utf8_general_ci";

The reason for using multi-dimensional arrays is to allow you to store multiple connected value settings at will. Example: If you run multiple environments (development, production, test, etc...), you can create independent connection groups for each environment and switch directly between groups. For example, to set up a "test" environment, you can do this:

$db['test']['hostname'] = "localhost";
$db['test']['username'] = "root";
$db['test']['password'] = "";
$db['test']['database'] = "database_name";
$db['test']['dbdriver'] = "mysql";
$db['test']['dbprefix'] = "";
$db['test']['pconnect'] = TRUE;
$db['test']['db_debug'] = FALSE;
$db['test']['cache_on'] = FALSE;
$db['test']['cachedir'] = "";
$db['test']['char_set'] = "utf8";
$db['test']['dbcollat'] = "utf8_general_ci";

Then, to tell the system to use the "test" group, you can set the variable located in the configuration file:

$active_group = "test";

Note: The name of "test" is arbitrary, which allows you to set it freely. Our main connection uses the name "default" by default. Of course, you can give it a more meaningful name based on your project. .

Active Record

The Active Record class can be set globally through the $active_record variable in the database configuration file (allow/disable TRUE/FALSE (boolean)). If you don’t use this class, you can set the variable value to FALSE to reduce the consumption of computer resources during database class initialization. $active_record = TRUE;

Note: Some CodeIgniter classes, such as Sessions, require Active Records support when executing some functions.

Parameter analysis:

• hostname - The hostname of the database, usually located on the local machine, which can be expressed as "localhost".
• username - the username that needs to be connected to the database.
• password - the password to log in to the database.
• database - the name of the database you need to connect to.
• dbdriver - database type. Such as: mysql, postgres, odbc, etc. Must be lowercase letters.
• dbprefix - The prefix for the data table when running Active Record queries, which allows multiple CodeIgniter programs to be installed on a database.
• pconnect - TRUE/FALSE (boolean) - Use persistent connections.
• db_debug - TRUE/FALSE (boolean) - Display database error messages.
• cache_on - TRUE/FALSE (boolean) - Whether the database query cache is turned on. For details, please see the database cache class.
• cachedir - The absolute path of the server where the database query cache directory is located.
• char_set - The character set used when communicating with the database.
• dbcollat ​​- Character collation used when communicating with the database.
• port - Database port number. Currently only used by the Postgres driver. To use this value, you should add a line of code to the database configuration array.

Record it for easy reference.

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