The PDO class

(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.1.0)

Introduction

Represents a connection between PHP and a database server.

Class synopsis

PDO {

public __construct ( string $dsn [, string $username [, string $password [, array $options ]]] )

public bool beginTransaction ( void )

public bool commit ( void )

public mixed errorCode ( void )

public array errorInfo ( void )

public int exec ( string $statement )

public mixed getAttribute ( int $attribute )

public static array getAvailableDrivers ( void )

public bool inTransaction ( void )

public string lastInsertId ([ string $name = NULL ] )

public PDOStatement prepare ( string $statement [, array $driver_options = array() ] )

public PDOStatement query ( string $statement )

public string quote ( string $string [, int $parameter_type = PDO::PARAM_STR ] )

public bool rollBack ( void )

public bool setAttribute ( int $attribute , mixed $value )

}

PDO::beginTransaction — Initiates a transaction
PDO::commit — Commits a transaction
PDO::__construct — Creates a PDO instance representing a connection to a database
PDO::errorCode — Fetch the SQLSTATE associated with the last operation on the database handle
PDO::errorInfo — Fetch extended error information associated with the last operation on the database handle
PDO::exec — Execute an SQL statement and return the number of affected rows
PDO::getAttribute — Retrieve a database connection attribute
PDO::getAvailableDrivers — Return an array of available PDO drivers
PDO::inTransaction — Checks if inside a transaction
PDO::lastInsertId — Returns the ID of the last inserted row or sequence value
PDO::prepare — Prepares a statement for execution and returns a statement object
PDO::query — Executes an SQL statement, returning a result set as a PDOStatement object
PDO::quote — Quotes a string for use in a query.
PDO::rollBack — Rolls back a transaction
PDO::setAttribute — Set an attribute

User Contributed Notes

Megaloman

7 years ago


"And storing username/password inside class is not a very good idea for production code."

Good idea is to store database connection settings in *.ini files but you have to restrict access to them. For example this way:

my_setting.ini:
[database]
driver = mysql
host = localhost
;port = 3306
schema = db_schema
username = user
password = secret

Database connection:
<?php
class MyPDO extends PDO
{
    public function __construct($file = 'my_setting.ini')
    {
        if (!$settings = parse_ini_file($file, TRUE)) throw new exception('Unable to open ' . $file . '.');
        
        $dns = $settings['database']['driver'] .
        ':host=' . $settings['database']['host'] .
        ((!empty($settings['database']['port'])) ? (';port=' . $settings['database']['port']) : '') .
        ';dbname=' . $settings['database']['schema'];
        
        parent::__construct($dns, $settings['database']['username'], $settings['database']['password']);
    }
}
?>

Database connection parameters are accessible via human readable ini file for those who screams even if they see one PHP/HTML/any_other command.

kcleung at kcleung dot no-ip dot org

5 years ago


Here is an singleton PDO example:

###### config.ini ######
db_driver=mysql
db_user=root
db_password=924892xp

[dsn]
host=localhost
port=3306
dbname=localhost

[db_options]
PDO::MYSQL_ATTR_INIT_COMMAND=set names utf8

[db_attributes]
ATTR_ERRMODE=ERRMODE_EXCEPTION
############

<?php class Database {
    private static $link = null ;

    private static function getLink ( ) {
        if ( self :: $link ) {
            return self :: $link ;
        }

        $ini = _BASE_DIR . "config.ini" ;
        $parse = parse_ini_file ( $ini , true ) ;

        $driver = $parse [ "db_driver" ] ;
        $dsn = "${driver}:" ;
        $user = $parse [ "db_user" ] ;
        $password = $parse [ "db_password" ] ;
        $options = $parse [ "db_options" ] ;
        $attributes = $parse [ "db_attributes" ] ;

        foreach ( $parse [ "dsn" ] as $k => $v ) {
            $dsn .= "${k}=${v};" ;
        }

        self :: $link = new PDO ( $dsn, $user, $password, $options ) ;

        foreach ( $attributes as $k => $v ) {
            self :: $link -> setAttribute ( constant ( "PDO::{$k}" )
                , constant ( "PDO::{$v}" ) ) ;
        }

        return self :: $link ;
    }

    public static function __callStatic ( $name, $args ) {
        $callback = array ( self :: getLink ( ), $name ) ;
        return call_user_func_array ( $callback , $args ) ;
    }
} ?>

<?php // examples
$stmt = Database :: prepare ( "SELECT 'something' ;" ) ;
$stmt -> execute ( ) ;
var_dump ( $stmt -> fetchAll ( ) ) ;
$stmt -> closeCursor ( ) ;
?>

williambarry007 at gmail dot com

4 years ago


PDO and Dependency Injection

Dependency injection is good for testing.  But for anyone wanting various data mapper objects to have a database connection, dependency injection can make other model code very messy because database objects have to be instantiated all over the place and given to the data mapper objects.

The code below is a good way to maintain dependency injection while keeping clean and minimal model code.

<?php

class DataMapper
{
    public static $db;
    
    public static function init($db)
    {
        self::$db = $db;
    }
}

class VendorMapper extends DataMapper
{
    public static function add($vendor)
    {
        $st = self::$db->prepare(
            "insert into vendors set
            first_name = :first_name,
            last_name = :last_name"
        );
        $st->execute(array(
            ':first_name' => $vendor->first_name,
            ':last_name' => $vendor->last_name
        ));
    }
}

// In your bootstrap
$db = new PDO(...);
DataMapper::init($db);

// In your model logic
$vendor = new Vendor('John', 'Doe');
VendorMapper::add($vendor);

?>

schizo_mind at hotmail dot com

7 years ago


<?php

class PDOConfig extends PDO {

    

    private $engine;

    private $host;

    private $database;

    private $user;

    private $pass;

    

    public function __construct(){

        $this->engine = 'mysql';

        $this->host = 'localhost';

        $this->database = '';

        $this->user = 'root';

        $this->pass = '';

        $dns = $this->engine.':dbname='.$this->database.";host=".$this->host;

        parent::__construct( $dns, $this->user, $this->pass );

    }

}

?>

thz at plista dot com

2 years ago


Starting with PHP 5.4 you are unable to use persistent connections when you have your own database class derived from the native PDO class. If your code uses this combination, you will encounter segmentation faults during the cleanup of the PHP process.
You can still use _either_ a derived PDO class _or_ persistent connections.

For more information, please see this bug report: https://bugs.php.net/bug.php?id=63176

anrdaemon at freemail dot ru

7 years ago


Keep in mind, you MUST NOT use 'root' user in your applications, unless your application designed to do a database maintenance.

And storing username/password inside class is not a very good idea for production code. You would need to edit the actual working code to change settings, which is bad.

rumsg at mail dot ru

11 months ago


$DB = new PDO('mysql:host=127.0.0.1;port=3306;dbname=anexis_new;charset=UTF8;','root','password', array(PDO::ATTR_PERSISTENT=>true));
$DB->query("SET NAMES utf8;");

sideshowAnthony at googlemail dot com

9 months ago


Here is a cheeky PDO helper class to get you started . . .

define('DB_MAIN', 'localhost|user1|pa55word|db1');

// Connect to database db1
$db = new my_db(DB_MAIN);

// Request "SELECT * FROM table1 WHERE a=16 AND b=22"
// Get an array of stdClass's
$rows = $db->fetchAll('SELECT * FROM table1 WHERE a=? AND b=?', 16, 22);

class my_db{

    private static $databases;
    private $connection;

    public function __construct($connDetails){
        if(!is_object(self::$databases[$connDetails])){
            list($host, $user, $pass, $dbname) = explode('|', $connDetails);
            $dsn = "mysql:host=$host;dbname=$dbname";
            self::$databases[$connDetails] = new PDO($dsn, $user, $pass);
        }
        $this->connection = self::$databases[$connDetails];
    }
    
    public function fetchAll($sql){
        $args = func_get_args();
        array_shift($args);
        $statement = $this->connection->prepare($sql);        
        $statement->execute($args);
         return $statement->fetchAll(PDO::FETCH_OBJ);
    }
}

The PDO class

Introduction

Class synopsis

Table of Contents

User Contributed Notes