php获取mysql行数

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

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

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

$sql = "SELECT COUNT(*) as total_rows FROM table_name";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    $row = $result->fetch_assoc();
    echo "总行数: " . $row["total_rows"];
} else {
    echo "0 行";
}

$conn->close();
?>

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

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

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

$sql = "SELECT * FROM table_name";
$result = $conn->query($sql);

if ($result) {
    echo "总行数: " . $result->num_rows;
} else {
    echo "查询失败";
}

$conn->close();
?>

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

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

    $sql = "SELECT * FROM table_name";
    $stmt = $conn->prepare($sql);
    $stmt->execute();

    echo "总行数: " . $stmt->rowCount();
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

$conn = null;
?>