Performance note to those who wonder. I performed a test where first of all inserted about 30,000 posts with one PK:id and a varchar(20), where the varchar data was md5-hash for the current iterator value just to fill with some data.

The test was performed on a dedicated ubuntu 7.04 server with apache2/php5/mysql5.0 running on Athlon 64 - 3000+ with 512MB of RAM. The queries where tested with a for-loop from 0 to 30000 first with:

<?php
for ( $i = 0; $i <= 30000; ++$i )
{
    $result = $mysqli->query("SELECT * FROM test WHERE id = $i");
    $row = $result->fetch_row();
    echo $row[0]; //prints id
}
?>

which gave a page-load time of about 3.3seconds avarage, then with this loop:

<?php
$stmt = $mysqli->prepare("SELECT * FROM test WHERE id = ?");
for ( $i = 0; $i <= 30000; ++$i )
{
    $stmt->bind_param("i", $i);
    $stmt->execute();
    $stmt->bind_result($id, $md5);
    $stmt->fetch();
    echo $id;
}
$stmt->close();
?>

and the avarage page-load was lowered by 1.3sec, which means about 2.0 sec avarage! Guess the performance difference could be even greater on a more complex/larger table and more complex SQL-queries.