(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.1.0)
代表 PHP 和数据库服务之间的一个连接
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' );
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);
}
}
$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;");
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
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);
?>
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 ( ) ) ;
$stmt -> closeCursor ( ) ;
?>
"And storing username/password inside class is not a very good idea for production code."
Good idea is to store database connection settings in *.ini files but you have to restrict access to them. For example this way:
my_setting.ini:
[database]
driver = mysql
host = localhost
;port = 3306
schema = db_schema
username = user
password = secret
Database connection:
<?php
class MyPDO extends PDO
{
public function __construct($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.
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.
<?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 );
}
}
?>