我創建了這段代碼，我在其中創建了一個資料庫實體并使用它。現在我正在嘗試將代碼轉換為靜態形式，但我不能。
$pdo = new PDO('sqlite:src/chinook.db');
$sql = "CREATE TABLE IF NOT EXISTS uzivatele(
uzivatelId INTEGER PRIMARY KEY,
jmeno TEXT,
prijmeni TEXT,
body INTEGER
);";
$statement = $pdo->prepare($sql);
$statement->execute();
function dropTable($pdo,$name)
{
$sql = "DROP TABLE $name";
$statement = $pdo->prepare($sql);
$statement->execute();
}
...
static 這就是我為 pdo 實作一個類的方式（根據手冊），我想實作靜態方法，例如 createTable，但我不能重做
class Db
{
protected static $pdo = null;
public static function get(): \PDO
{
return self::$pdo ?? (self::$pdo = new \PDO(
'sqlite:hw-06.db',
null,
null,
[
\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION
]
));
}
}
use App\Db;
class Account
{
...
public static function createTable(): void
{
$db = Db::get();
$sql = "CREATE TABLE IF NOT EXISTS uzivatele(
uzivatelId INTEGER PRIMARY KEY,
jmeno TEXT,
prijmeni TEXT,
body INTEGER
);";
$statement = $db->prepare($sql);
$statement->execute();
}
index.php 帳號::createTable();
uj5u.com熱心網友回復：
如果你想實作一個簡單的單例，你可以使用“getInstance()”的概念，并結合“__callStatic”和“call_user_func_array”使一個PDO函式也變成靜態的，所有的PDO和資料庫類函式都會變成靜態的：
<?php
declare(strict_types = 1);
/*
* PDO database class - only one connection alowed
*/
final class Database
{
/**
* @var PDO $connection The connection
*/
private $connection;
/**
* @var Database $instance The single instance
*/
private static $instance;
/**
* @var string $engine The engine of connection
*/
private $engine = 'sqlite:persistence.db'; // sqlite::memory:
/**
* @var array $options Default option to PDO connection
*/
private $options = [
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_EMULATE_PREPARES => false
];
/**
* Private constructor to prevent instance
*
* @throws \Throwable
* @return void
*/
private function __construct()
{
try {
$this->connection = new PDO($this->engine, null, null, $this->options);
}
catch (\Throwable $error) {
error_log("{$error->getMessage()}");
}
}
/**
* Get an instance of the Database
*
* @return PDO
*/
private static function getInstance(): PDO
{
// If no instance then make one
if (!self::$instance) {
self::$instance = new self;
}
return self::$instance->connection;
}
/**
* Transpiler of static methods for PDOStatements
*
* @var string $method The PDO static method
* @var array $args
* @return string|PDOStatement
*/
public static function __callStatic(string $method, array $args)
{
return call_user_func_array(array(self::getInstance(), $method), $args);
}
/**
* Destroying PDO connection
*
* @return void
*/
public function __destruct()
{
if (!empty($this->connection)) {
unset($this->connection);
}
}
/**
* Magic method clone is empty to prevent duplication of connection
*/
public function __clone() { }
public function __wakeup() { }
public function __toString() { }
}
在那里使用：
<?php
require_once __DIR__ . '/Database.php';
Database::exec('CREATE TABLE IF NOT EXISTS uzivatele (
uzivatelId INTEGER PRIMARY KEY,
jmeno TEXT,
prijmeni TEXT,
body INTEGER
);');
Database::exec("INSERT INTO uzivatele (jmeno, prijmeni, body) VALUES ('test', 'test', 1);");
var_dump(Database::lastInsertId());
$stmt = Database::prepare("SELECT * FROM uzivatele;");
$stmt->execute();
$data = $stmt->fetchAll();
var_dump($data);
請注意，“準備好的陳述句物件”仍然是物件！
我認為將資料庫連接用作靜態連接沒有任何問題，如果它們不并行使用，則沒有問題，它甚至減少了與資料庫創建許多連接的開銷。但要小心，在某些情況下它可能沒有好處，因為在代碼不是由 CGI 或 FastCGI 而是由包裝器執行的情況下，它可能會導致速度減慢甚至出現問題！
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