如何设置我的 php 代码结果的样式 - How can I style my php code result?

How can I style my php code result?

我写了这段代码，我想用css来设置它的样式。我为它添加了样式，但出现了相同的结果，任何身体都可以提供帮助.

<p>
<phpcode> 
<?php           
$term = mysql_real_escape_string($_REQUEST['term']);
$servername = "localhost";
$username = "***********";
$password = "***********";
$dbname = "*************";
$conn = new mysqli($servername, $username, $password, $dbname); 
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}   
$sql = "SELECT Install ,  power , RPM FROM SN WHERE serial = '$term'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "serial number: " . $term.'<br>';
        echo "installation: " . $row["Install"].'<br>';
        echo "power: " . $row["power"].'<br>';
        echo "RPM: " . $row["RPM"].'<br>';
    }
} else {
    echo "no result";
}
$conn->close();         
?> 
</phpcode>
</p>

<style>
    .results div:nth-of-type(1){
        color:red;
        background:blue;
        font-size:3rem;
    }
    .results div:nth-of-type(2){
        color:blue; 
        background:yellow;
        font-size:2rem;
    }
    .results div:nth-of-type(3){
        color:green;
        background:orange;
        font-size:1rem;
    }
    .results div:nth-of-type(4){
        color:orange;
        background:black;
        font-size:0.5rem;   
    }
</style>


    while( $row = $result->fetch_assoc() ) {
        echo "
        <div class='results'>
            <div>serial number:{$term}</div>
            <div>installation:{$row['install']}</div>
            <div>power:{$row['power']}</div>
            <div>rpm:{$row['rpm']}</div>
        </div>";
    }