php后台框架的数据库连接方式

PHP后台框架通常使用PDO（PHP Data Objects）或者MySQLi（MySQL Improved）这两种方式来连接数据库。

1. PDO连接方式：

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "dbname";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
} catch(PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

2. MySQLi连接方式：

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "dbname";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";

这两种连接方式都可以用来连接MySQL数据库，但PDO更加灵活和方便，支持多种数据库类型，而MySQLi只支持MySQL数据库。在实际开发中，可以根据具体需求来选择适合自己项目的数据库连接方式。