PDO 类

thz at plista dot com (2013-06-14 13:25:45)

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

williambarry007 at gmail dot com (2011-10-12 13:10:27)

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);

?>

RockMeAmadeus (2010-08-25 10:44:24)

PDO::getAvailableDrivers is the only PDO static method so it needs a double colon. The other PDO methods are used by an object, so they should use the -> syntax.
* 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->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

kcleung at kcleung dot no-ip dot org (2010-05-02 15:47:51)

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 ( ) ;
?>

Megaloman (2009-02-18 07:03:48)

"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.

anrdaemon at freemail dot ru (2008-08-22 01:16:27)

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.

schizo_mind at hotmail dot com (2008-07-28 10:00:16)

<?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 );
    }
}
?>