PHP MYSQL HighScores list not working - php

Question

I have a table name "scores"
+----+-------+-------+-------------------+
| id | score | level | username |
+----+-------+-------+-------------------+
| 1 | 65 | one | dustyrydberg |
| 2 | 56 | one | dustyrydberg |
| 3 | 34 | one | pointedshrill |
| 4 | 50 | one | witchrage |
| 5 | 41 | one | spacetimeken |
| 6 | 44 | one | harperhetton |
| 7 | 65 | one | witchrage |
| 8 | 70 | one | paladino |
| 9 | 50 | one | chimpanzer |
| 10 | 22 | one | yahooligan |
| 11 | 672 | one | blueCrow |
| 12 | 120 | one | sleepyDolphin |
| 13 | 43 | one | gothicNightingale |
| 14 | 22 | one | phonyPuppy |
| 15 | 23 | one | phonyPuppy |
| 16 | 24 | one | phonyPuppy |
| 17 | 31 | one | darlingFairy |
| 18 | 36 | one | starkVoid |
+----+-------+-------+-------------------+
I am trying to list the top 10 highscores without duplication of usernames. I am doing this using php and mysql. I have a functions.php file which includes the following function:
function find_all_scores() {
global $connection;
$query = "SELECT MIN(score), username ";
$query .= "FROM scores ";
$query .= "GROUP BY username ";
$query .= "ORDER BY MIN(score) ASC";
$score_set = mysqli_query($connection, $query);
confirm_query($score_set);
return $score_set;
}
Which is called on in the all_highscores.php file
<?php require_once("../includes/session.php"); ?>
<?php require_once("../includes/db_connection.php"); ?>
<?php require_once("../includes/functions.php"); ?>
<?php
$score_set = find_all_scores();
$ranking = 1;
?>
<?php $layout_context = "score"; ?>
<?php include("../includes/layouts/header.php"); ?>
<div id="main">
<div id="navigation">
</div>
<div id="page">
<?php echo message(); ?>
<h2>Your Highscores</h2>
<p>Here are <?php echo htmlentities($_SESSION["username"]); ?>'s best scores.</p>
<table>
<tr>
<th style="text-align: left; width: 200px;">Position</th>
<th style="text-align: left; width: 200px;">Username</th>
<th style="text-align: left; width: 200px;">Level</th>
<th colspan="2" style="text-align: left;">Score</th>
</tr>
<?php while($score = mysqli_fetch_assoc($score_set)) { ?>
<tr>
<td><?php echo $ranking; ?></td>
<td><?php echo htmlentities($score["username"]); ?></td>
<td><?php echo htmlentities($score["level"]); ?></td>
<td><?php echo htmlentities($score["score"]); ?></td>
<?php
$ranking = $ranking + 1; /* INCREMENT RANKING BY 1 */
?>
</tr>
<?php } ?>
</table>
</div>
</div>
<?php
// 4. Release returned data
//mysqli_free_result($result);
?>
<?php include("../includes/layouts/footer.php"); ?>
However I keep ending up with either a query failure or nothing displays in the HTML browser. Please help!