{"db": {"user": "root","password": "xxxx","host": "10.2.3.4","port": "3306","dbname": "bookstore"}
}

<?phpnamespace Bookstore\Utils;use Bookstore\Exceptions\NotFoundException;require_once __DIR__ . '/NotFoundException.php';class Config {private $data;//类静态变量,保证变量唯一性private static $instance;//构造函数私有化,类外部不可以调用.private function __construct() {$json = file_get_contents(__DIR__ . '/app.json');$this->data = json_decode($json, true);}//单例模式,保证只实例化一个类.public static function getInstance() {if (self::$instance == null) {//是可以自己实例化自己的.self::$instance = new Config();}return self::$instance;}public function get($key) {if (!isset($this->data[$key])) {throw new NotFoundException("Key $key not in config.");}return $this->data[$key];}
}
?>

<?php
//使用命名空间,易于在大型应用中管理和组织php类.use Bookstore\Utils\Config;//命名空间可以直接use,但如果这个命名空间没有在标准约定位置,且没有自动载入的话,需要使用require来手工定位一下.
require_once __DIR__ . '\Config.php';header("content-type:text/html;charset=utf-8");
$dbConfig = Config::getInstance()->get("db");$connStr = "mysql:host={$dbConfig['host']};port={$dbConfig['port']};dbname={$dbConfig['dbname']};charset=utf8";$db = new \PDO($connStr,    $dbConfig['user'], $dbConfig['password']);
$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);$query = 'SELECT * FROM book WHERE author = :author';
$statement = $db->prepare($query);
$statement->bindValue('author', 'George Orwell');
$statement->execute();
$rows = $statement->fetchAll();
foreach ($rows as $row) {var_dump($row);
}
echo "<br/>";
$query = <<<SQL
INSERT INTO book(isbn, title, author, price)
VALUES(:isbn, :title, :author, :price)
SQL;
$statement = $db->prepare($query);
$params = ['isbn' => '9781413108614','title' => 'Iliad','author' => 'Homer','price' => 9.25
];
$statement->execute($params);
$result = $db->exec($query);
echo $db->lastInsertId();
echo "<br/>";function addBook(int $id, int $amount=1):void {$query = 'UPDATE book SET stock = stock + :n WHERE id = :id';$statement = $db->prepare($query);$statement->bindValue('id', $id);$statement->bindValue('n', $amount);if (!$statement->execute()) {throw new Exception($statement->errorInfo()[2]);}
}function addSale($db, int $userId, array $bookIds):void {$db->beginTransaction();try {$query = 'INSERT INTO sale(customer_id, date)'. 'VALUES(:id, NOW())';$statement = $db->prepare($query);if (!$statement->execute(['id'=> $userId])) {throw new Exception($statement->errorInfo()[2]);}$saleId = $db->lastInsertId();$query = 'INSERT INTO sale_book(book_id, sale_id)'. 'VALUES(:book, :sale)';$statement = $db->prepare($query);$statement->bindValue('sale', $saleId);foreach ($bookIds as $bookId) {$statement->bindValue('book', $bookId);if (!$statement->execute()) {throw new Exception($statement->errorInfo()[2]);}}$db->commit();} catch (Exception $e) {$db->rollback();throw $e;}
}try {addSale($db, 1, [1, 2, 300]);
} catch (Exception $e) {echo 'Error adding sale: ' . $e->getMessage();
}try {addSale($db, 1, [1, 2, 3]);
} catch (Exception $e) {echo 'Error adding sale: ' . $e->getMessage();
}?>

array(6) { ["id"]=> string(1) "1" ["isbn"]=> string(13) "9780882339726" ["title"]=> string(4) "1984" ["author"]=> string(13) "George Orwell" ["stock"]=> string(2) "12" ["price"]=> string(3) "8.7" } array(6) { ["id"]=> string(1) "3" ["isbn"]=> string(13) "9780736692427" ["title"]=> string(11) "Animal Farm" ["author"]=> string(13) "George Orwell" ["stock"]=> string(1) "8" ["price"]=> string(4) "4.06" }
0
Error adding sale: Cannot add or update a child row: a foreign key constraint fails (`bookstore`.`sale_book`, CONSTRAINT `sale_book_ibfk_2` FOREIGN KEY (`book_id`) REFERENCES `book` (`id`))