php 判断数据库有没有

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

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

// 检查连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询数据库列表
$sql = "SHOW DATABASES";
$result = $conn->query($sql);

$databaseExists = false;
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        if ($row['Database'] == 'your_database_name') {
            $databaseExists = true;
            break;
        }
    }
}

if ($databaseExists) {
    echo "数据库存在";
} else {
    echo "数据库不存在";
}

$conn->close();
?>

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

try {
    // 创建PDO连接
    $conn = new PDO("mysql:host=$servername", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 查询数据库列表
    $stmt = $conn->query("SHOW DATABASES");
    $databaseExists = false;
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        if ($row['Database'] == 'your_database_name') {
            $databaseExists = true;
            break;
        }
    }

    if ($databaseExists) {
        echo "数据库存在";
    } else {
        echo "数据库不存在";
    }
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

$conn = null;
?>