PHP如何查询mysql数据_PHP执行mysql查询的完整方法

$host = 'localhost';
$username = 'root';
$password = '';
$database = 'test_db';
<p>// 建立连接
$conn = mysqli_connect($host, $username, $password, $database);</p><p>// 检查连接
if (!$conn) {
die("连接失败: " . mysqli_connect_error());
}</p><p>// 执行查询
$sql = "SELECT id, name, email FROM users";
$result = mysqli_query($conn, $sql);</p><p>// 检查是否有结果
if (mysqli_num_rows($result) > 0) {
while($row = mysqli_fetch_assoc($result)) {
echo "ID: " . $row["id"]. " - 名字: " . $row["name"]. " - 邮箱: " . $row["email"]. "<br>";
}
} else {
echo "0 个结果";
}</p><p>// 关闭连接
mysqli_close($conn);</p>

$host = 'localhost';
$username = 'root';
$password = '';
$database = 'test_db';
<p>$conn = new mysqli($host, $username, $password, $database);</p><p>if ($conn->connect_error) {
die("连接失败: " . $conn->connect_error);
}</p><p>$sql = "SELECT id, name, email FROM users";
$result = $conn->query($sql);</p><p>if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
echo "ID: " . $row["id"]. " - 名字: " . $row["name"]. " - 邮箱: " . $row["email"]. "<br>";
}
} else {
echo "0 个结果";
}</p><p>$conn->close();</p>
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$host = 'localhost';
$dbname = 'test_db';
$username = 'root';
$password = '';
<p>try {
$pdo = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
// 设置错误模式为异常
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);</p><pre class='brush:php;toolbar:false;'>$sql = "SELECT id, name, email FROM users";
$stmt = $pdo->query($sql);

while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo "ID: " . $row["id"]. " - 名字: " . $row["name"]. " - 邮箱: " . $row["email"]. "<br>";
}

$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$_GET['id']]);
$user = $stmt->fetch();

$stmt = $pdo->prepare("SELECT * FROM users WHERE name = :name");
$stmt->execute([':name' => $name]);