The Database Package

Introduction

The Database package is designed to manage the operations of data management through the use of a generic database engine.

// Example for initialising a database driver in a custom application class.

use Joomla\Application\AbstractApplication;
use Joomla\Database;

class MyApplication extends AbstractApplication
{
	/**
	 * Database driver.
	 *
	 * @var    Database\DatabaseDriver
	 * @since  1.0
	 */
	protected $db;

	protected function doExecute()
	{
		// Do stuff
	}

	protected function initialise()
	{
		// Make the database driver.
		$dbFactory = new Database\DatabaseFactory;

		$this->db = $dbFactory->getDriver(
			$this->get('database.driver'),
			array(
				'host' => $this->get('database.host'),
				'user' => $this->get('database.user'),
				'password' => $this->get('database.password'),
				'port' => $this->get('database.port'),
				'socket' => $this->get('database.socket'),
				'database' => $this->get('database.name'),
			)
		);
	}
}

Escaping Strings and Input

Strings must be escaped before using them in queries (never trust any variable input, even if it comes from a previous database query from your own data source). This can be done using the escape and the quote method.

The escape method will generally backslash unsafe characters (unually quote characters but it depends on the database engine). It also allows for optional escaping of additional characters (such as the underscore or percent when used in conjunction with a LIKE clause).

The quote method will escape a string and wrap it in quotes, however, the escaping can be turned off which is desirable in some situations. The quote method will also accept an array of strings and return an array quoted and escaped (unless turned off) string.

function search($title)
{
	// Get the database driver from the factory, or by some other suitable means.
	$db = DatabaseDriver::getInstance($options);

	// Search for an exact match of the title, correctly sanitising the untrusted input.
	$sql1 = 'SELECT * FROM #__content WHERE title = ' . $db->quote($title);

	// Special treatment for a LIKE clause.
	$search = $db->quote($db->escape($title, true) . '%', false);
	$sql2 = 'SELECT * FROM #__content WHERE title LIKE ' . $search;

	if (is_array($title))
	{
		$sql3 = 'SELECT * FROM #__content WHERE title IN ('
			. implode(',', $db->quote($title)) . ')';
	}

	// Do the database calls.
}

In the first case, the title variable is simply escaped and quoted. Any quote characters in the title string will be prepended with a backslash and the whole string will be wrapped in quotes.

In the second case, the example shows how to treat a search string that will be used in a LIKE clause. In this case, the title variable is manually escaped using escape with a second argument of true. This will force other special characters to be escaped (otherwise you could set youself up for serious performance problems if the user includes too many wildcards). Then, the result is passed to the quote method but escaping is turned off (because it has already been done manually).

In the third case, the title variable is an array so the whole array can be passed to the quote method (this saves using a closure and a )

Shorthand versions are available the these methods:

• q can be used instead of quote
• qn can be used instead of quoteName
• e can be used instead of escape

These shorthand versions are also available when using the Database\DatabaseQuery class.

Iterating Over Results

The Database\DatabaseIterator class allows iteration over database results

$db = DatabaseDriver::getInstance($options);
$iterator = $db->setQuery(
	$db->getQuery(true)->select('*')->from('#__content')
)->getIterator();

foreach ($iterator as $row)
{
    // Deal with $row
}

It allows also to count the results.

$count = count($iterator);

Logging

Database\DatabaseDriver implements the Psr\Log\LoggerAwareInterface so is ready for intergrating with a logging package that supports that standard.

Drivers log all errors with a log level of LogLevel::ERROR.

If debugging is enabled (using setDebug(true)), all queries are logged with a log level of LogLevel::DEBUG. The context of the log include:

• sql : The query that was executed.
• category : A value of "databasequery" is used.

An example to log error by Monolog

Add this to composer.json

{
	"require" : {
		"monolog/monolog" : "1.*"
	}
}

Then we push Monolog into Database instance.

use Monolog\Logger;
use Monolog\Handler\StreamHandler;
use Monolog\Processor\PsrLogMessageProcessor;

// Create logger object
$logger = new Logger('sql');

// Push logger handler, use DEBUG level that we can log all information
$logger->pushHandler(new StreamHandler('path/to/log/sql.log', Logger::DEBUG));

// Use PSR-3 logger processor that we can replace {sql} with context like array('sql' => 'XXX')
$logger->pushProcessor(new PsrLogMessageProcessor);

// Push into DB
$db->setLogger($logger);
$db->setDebug(true);

// Do something
$db->setQuery('A WRONG QUERY')->execute();

This is the log file:

[2014-07-29 07:25:22] sql.DEBUG: A WRONG QUERY {"sql":"A WRONG QUERY","category":"databasequery","trace":[...]} []
[2014-07-29 07:36:01] sql.ERROR: Database query failed (error #42000): SQL: 42000, 1064, You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'A WRONG QUERY' at line 1 {"code":42000,"message":"SQL: 42000, 1064, You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'A WRONG QUERY' at line 1"} []

Installation via Composer

Add "joomla/database": "~2.0" to the require block in your composer.json and then run composer install.

{
	"require": {
		"joomla/database": "~2.0"
	}
}

Alternatively, you can simply run the following from the command line:

composer require joomla/database "~2.0"

If you want to include the test sources, use

composer require --prefer-source joomla/database "~2.0"