PHP中mysqli_num_rows如何使用

mysqli_num_rows函数用于获得结果集中的行数。使用方法以下：

1.创建数据库连接：

$conn = mysqli_connect("localhost", "username", "password", "database_name");
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}

2.履行SQL查询并获得结果集：

$sql = "SELECT * FROM table_name";
$result = mysqli_query($conn, $sql);

3.使用mysqli_num_rows函数获得结果集中的行数：

$row_count = mysqli_num_rows($result);
echo "行数：" . $row_count;

完全示例代码以下：

$conn = mysqli_connect("localhost", "username", "password", "database_name");
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}

$sql = "SELECT * FROM table_name";
$result = mysqli_query($conn, $sql);
$row_count = mysqli_num_rows($result);
echo "行数：" . $row_count;

mysqli_close($conn);

注意：在使用mysqli_num_rows函数之前，需要确保已履行了SQL查询并获得了结果集。