pdo检查数据库是否存在

<?php
header("Content-Type: text/html;charset=utf-8");
error_reporting(E_ALL | E_STRICT);

$param_arr = getopt('h:u:p:d:');

$host     = $param_arr['h'] ?: '127.0.0.1';
$user     = $param_arr['u'];
$pwd      = $param_arr['p'];
$dbname   = $param_arr['d'];

// 判断数据库是否存在
try {
    $conn = new PDO("mysql:host=$host", $user, $pwd);
    // 设置 PDO 错误模式为异常 
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $sql = "show databases;";
    // 使用 exec() ，因为没有结果返回 
    $res = $conn->query($sql);
    $res = $res->fetchAll(PDO::FETCH_ASSOC);
    $database_list = [];
    foreach($res as $k => $v) {
        $database_list[] = $v['Database'];
    }
    if (in_array($dbname,$database_list)) {
        echo 1; // 存在
    } else {
        echo 2; // 不存在
    }
    $conn = null;
    return;
} catch (PDOException $e) {
    // echo $sql . "<br>" . $e->getMessage();
    echo 0;
    $conn = null;
    return;
}