基本的 PDO 连接和检索

Created: November-22, 2018

自 PHP 5.0 起， PDO 已作为数据库访问层使用。它与数据库无关，因此以下连接示例代码只需更改 DSN 即可适用于任何受支持的数据库。

// First, create the database handle

//Using MySQL (connection via local socket):
$dsn = "mysql:host=localhost;dbname=testdb;charset=utf8";

//Using MySQL (connection via network, optionally you can specify the port too):
//$dsn = "mysql:host=127.0.0.1;port=3306;dbname=testdb;charset=utf8";

//Or Postgres
//$dsn = "pgsql:host=localhost;port=5432;dbname=testdb;";

//Or even SQLite
//$dsn = "sqlite:/path/to/database"

$username = "user";
$password = "pass";
$db = new PDO($dsn, $username, $password);

// setup PDO to throw an exception if an invalid query is provided
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

// Next, let's prepare a statement for execution, with a single placeholder
$query = "SELECT * FROM users WHERE class = ?";
$statement = $db->prepare($query);

// Create some parameters to fill the placeholders, and execute the statement
$parameters = [ "221B" ];
$statement->execute($parameters);

// Now, loop through each record as an associative array
while ($row = $statement->fetch(PDO::FETCH_ASSOC)) {
    do_stuff($row);
}

该 prepare 函数创建从查询字符串 PDOStatement 对象。在此返回的对象上执行查询和检索结果。如果发生故障，该功能要么返回 false，要么抛出一个 exception（取决于 PDO 连接的配置方式）。