Classificando um array PHP em colunas

$list = mysql_query("SELECT * FROM people ORDER BY class_year1, last_name",$db);

$decade = false;
while ($thearray = mysql_fetch_array($list)) {

    // checks if decade is diferent, if so updates and prints it
    if( $decade != substr($thearray['class_year'], 2, 1) ) {
        // every time we change decade we print a DIV
        if($decade!==false) echo "</div>";

        $decade = substr($thearray['class_year'], 2, 1);
        echo "<div><h3>19".$decade."0</h3>";
    }

    // prints info for each row
    echo "<div>".$thearray['name']." - ".$thearray['class_year1']."<br />".$thearray['description']."</div>"; 

}

// we print another DIV in the end to close it right
echo "</div>";