La clase PDO

(PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo >= 0.1.0)

Introducción

Representa una conexión entre PHP y un servidor de bases de datos.

Sinopsis de la Clase

class PDO {

public __construct(
    string $dsn,
    string $username = ?,
    string $password = ?,
    array $options = ?
)

public beginTransaction(): bool

public commit(): bool

public static connect(
    string $dsn,
    ?string $username = null,
    #[\SensitiveParameter] ?string $password = null,
    ?array $options = null
): static

public errorCode(): mixed

public errorInfo(): array

public exec(string $statement): int

public getAttribute(int $attribute): mixed

public static getAvailableDrivers(): array

public inTransaction(): bool

public lastInsertId(string $name = null): string

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

public query(string $statement): PDOStatement

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

public rollBack(): bool

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

}

Tabla de contenidos

PDO::beginTransaction — Inicia una transacción
PDO::commit — Consigna una transacción
PDO::connect — Connect to a database and return a PDO subclass for drivers that support it
PDO::__construct — Crea una instancia de PDO que representa una conexión a una base de datos
PDO::errorCode — Obtiene un SQLSTATE asociado con la última operación en el manejador de la base de datos
PDO::errorInfo — Obtiene información extendida del error asociado con la última operación del manejador de la base de datos
PDO::exec — Ejecuta una sentencia SQL y devuelve el número de filas afectadas
PDO::getAttribute — Devuelve un atributo de la conexión a la base de datos
PDO::getAvailableDrivers — Devuelve un array con los controladores de PDO disponibles
PDO::inTransaction — Comprueba si una transacción está activa
PDO::lastInsertId — Devuelve el ID de la última fila o secuencia insertada
PDO::prepare — Prepara una sentencia para su ejecución y devuelve un objeto sentencia
PDO::query — Ejecuta una sentencia SQL, devolviendo un conjunto de resultados como un objeto PDOStatement
PDO::quote — Entrecomilla una cadena de caracteres para usarla en una consulta
PDO::rollBack — Revierte una transacción
PDO::setAttribute — Establece un atributo

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User Contributed Notes 6 notes

down

Megaloman ¶

15 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.

down

anrdaemon at freemail dot ru ¶

16 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.

down

williambarry007 at gmail dot com ¶

13 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);

?>

down

sinri at everstray dot com ¶

7 years ago

For some Database Environment, such as Aliyun DRDS (Distributed Relational Database Service), cannot process preparing for SQL. 
For such cases, the option `\PDO::ATTR_EMULATE_PREPARES` should be set to true. If you always got reports about "Failed to prepare SQL" while this option were set to false, you might try to turn on this option to emulate prepares for SQL.

down

thz at plista dot com ¶

11 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

down

Anonymous ¶

7 years ago

I personnaly create a new instance of PDO like this : 

$dbDatas = parse_ini_file( DB_FILE );
 $dbOptions = [
 \PDO::ATTR_DEFAULT_FECTH_MODE => \PDO::FETCH_OBJ,
 \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION
 ];

 $dsn = sprintf( 'mysql:dbname=%s;host=%s', $dbDatas['dbname'],
$dbDatas['host'] );
 
 $this->cn = new \PDO( $dsn, $dbDatas['user'], $dbDatas['password'],
$dbOptions );
 $this->cn->exec( 'SET CHARACTER SET UTF8' );

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