PHP PDO：我的PHP可以更清洁/更高效吗？

Question

So I've finally decided to update my PHP for the year 2012 by learning to use PHP's PDO. So far everything is going great, however I don't know if the way I'm going about it is really the best way of doing it.

In this example I am querying my database to display posts users have made, and then displaying 2 comments for each post. So basically what I'm doing is grabbing my posts, looping it out, then in that loop I query the database for the top two comments for every post. However before I run around and start using this all year, I figured I'd see if there is a cleaner method of doing this.

So if anyone could spare a moment to look over this small block of code and let me know if there is a cleaner and perhaps more efficient way of doing this I'd really appreciate it. Feel free to nitpick!

<?php
$hostname = 'localhost';
$username = 'root';
$password = 'root';
$database = 'database';
try {
    $dbh = new PDO("mysql:host=$hostname;dbname=$database", $username, $password);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

//Get Posts
    $stmt = $dbh->prepare("SELECT * FROM posts");
    $stmt->execute();
    $result = $stmt->fetchAll();
    }
catch(PDOException $e)
    {
    echo $e->getMessage();
    }

//Loop through each post
foreach($result as $row) {

echo $row['post'];

//Get comments for this post
    $pid = $row['id'];
    $stmt = $dbh->prepare("SELECT * FROM comments WHERE pid = :pid LIMIT 2");
    $stmt->bindParam(':pid', $pid, PDO::PARAM_STR);
    $stmt->execute();
    $c_result = $stmt->fetchAll();

//Loop through comments
foreach($c_result as $com) {

echo $com['comment'];

    }
}
//Close connection
$dbh = null;
?>

Answer 1

Well, it is actually 2 questions.

.1. For the code you are using, it is quite ugly. Using raw API functions always makes your code ugly, boring and repetitive. To run just one query took you FIVE lines!
Don't you think that just one line would be better? Line consists of only meaningful operators?

$comments = $db->getAll("SELECT * FROM comments WHERE pid = :pid LIMIT 2",$row['id']);

.2. For the algorithm - it is quite okay.
Assuming you are * not going to loop over all your database, but merely request only 10-20 posts per page, additional 10-20 primary-key based lookups won't slow your application much.

.3. Bonus track.
thing you really may want to consider is a "business logic/presentation logic separation". Why not to get all your data first and only than starting an output? it will make your code way more clean.