本地mysql数据库db_test里已建有表friend，数据库的连接用户为root，端口为默认端口，密码为空。friend表字段为：id,name,age,gender,phone,email。请使用PHP连接mysql，查询friend表里age>20的所有字段，输出查询结果以及结果的记录总数。

好的，这里是PHP连接mysql，查询friend表里age>20的所有字段的代码：

<?php
// 连接数据库
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "db_test";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// 查询数据
$sql = "SELECT * FROM friend WHERE age > 20";
$result = mysqli_query($conn, $sql);

// 输出查询结果
if (mysqli_num_rows($result) > 0) {
    echo "<table border='1'>";
    echo "<tr><th>ID</th><th>Name</th><th>Age</th><th>Gender</th><th>Phone</th><th>Email</th></tr>";

    while ($row = mysqli_fetch_assoc($result)) {
        echo "<tr>";
        echo "<td>" . $row["id"] . "</td>";
        echo "<td>" . $row["name"] . "</td>";
        echo "<td>" . $row["age"] . "</td>";
        echo "<td>" . $row["gender"] . "</td>";
        echo "<td>" . $row["phone"] . "</td>";
        echo "<td>" . $row["email"] . "</td>";
        echo "</tr>";
    }

    echo "</table>";
    echo "Total records: " . mysqli_num_rows($result);
} else {
    echo "0 results";
}

// 关闭连接
mysqli_close($conn);
?>

运行这段代码，就可以输出查询结果以及结果的记录总数了。