PHP 连接本地mysql

<?php
echo microtime(true);
?>

<?php
$servername = "localhost";
$username = "root";
$password = "";

// 创建连接
$conn = new mysqli($servername, $username, $password);

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}
echo "连接成功";
?>

<?php
$servername = "localhost";
$username = "root";
$password = "";

try {
    $conn = new PDO("mysql:host=$servername;", $username, $password);
    echo "连接成功";
}
catch(PDOException $e)
{
    echo $e->getMessage();
}
?>