Having difficulties sorting data from mysql query using php - php

Question

This code is used to get a specific list of ID's from one table, then use those ID's to get the information from another table. Once I get all the information from the 2nd table, I am attempting to sort the data alphabetically based on a field in the 2nd table.
Example, I am getting the name based on a correlating ID and then want to display the entire result in alphabetical order by name (artist_name).
Here is the code I have. When I execute this without the sort(), it works fine but is not in alphabetical order. When I add the sort() in the 2nd while statement, the page looks the same but the name and other data do not display. The source code in the browser shows that the results are being accounted for but the sort must be preventing the variables or information from being displayed for some reason.
I haven't used a sort function before and I tried looking at some examples but couldn't really find something specific to my situation. Any and all help would be greatly appreciated. I have already looked at the PHP manual for sort so no need to send me a link to it ;-)
<?php $counter = 0;
$artistInfo = mysql_query("SELECT DISTINCT event_url_tbl.artist_id FROM event_url_tbl WHERE (SELECT cat_id FROM artist_tbl WHERE artist_tbl.artist_id = event_url_tbl.artist_id) = 1");
while ($aID = mysql_fetch_array($artistInfo))
{
$getArtistInfo = mysql_query("SELECT * FROM artist_tbl WHERE artist_id = '" . $aID['artist_id'] . "'");
while($artist = mysql_fetch_array($getArtistInfo))
{
sort($artist);?>
<a class="navlink" href="<?=HOST?><?=$artist['page_slug']?>/index.html">
<?=$artist['artist_name']?>
</a><br />
<?php }
}
?>

Answer 1

Your best bet, as a commenter mentioned, is to use an ORDER BY clause in SQL.
SELECT *
FROM artist_tbl
WHERE artist_id = XXX
ORDER BY artist_name ASC
The other commenter who suggested using PDO or mysqli is also correct, but that's a different issue.
To answer your specific question about sorting, according to the manual,
Blockquote Note: This function assigns new keys to the elements in array. It will remove any existing keys that may have been assigned, rather than just reordering the keys.
This means all of your array keys ('page_slug', 'artist_name', etc) are wiped out. So when you try to refer to them later, there is no data there.
Were you to use this method, you would want to use asort to sort an associative array.
However, you don't want to use sort here. What you're sorting is the variables for one row of data (one individual artists), not all of your artists. So if you think of each artist row as an index card full of data (name, id#, page slug, etc) all you're doing is moving those items around on the card. You're not reorganizing your card catalog.
Using an order by clause in the SQL statement (and rewriting in PDO) is your best bet.
Here is how I would rewrite it. I have to take some guesses at the SQL because I'm not 100% sure of your database structure and what you're specifically trying to accomplish, but I think this would work.
$query_str = "
SELECT
artist.name,
artist.page_slug
FROM
artist_tbl AS artist
INNER JOIN event_tbl AS event
ON event.artist_id = artist.artist_id
WHERE
artist.cat_id = 1
ORDER BY
artist.name ASC";
$db_obj = new PDO (/*Connection stuff*/);
$artists_sql = $db_obj->prepare ($query_str);
$artists_sql->execute ();
while ($artist = $artists_sql->fetch (PDO::FETCH_ASSOC)) {
$return_str .= "<a class='navlink' href='{HOST}
{$artist['page_slug']}/index.html'>
{$artist['artist_name']}</a><br/>";
}
echo $return_str;
In all honesty, I would probably create an artist class with a display_link method and use PDO's fetchObject method to instantiate the artists, but that's getting ahead of ourselves here.
For now I stuck with procedural code. I don't usually like to mix my HTML and PHP so I assign everything to a return string and echo it out at the end. But this is close to what you had, using one SQL query (in PDO - seriously worth starting to use if you're creating new code) that should give you a list of artists sorted by name and their associated page_slugs.

Answer 2

You could do all of this in one query:
SELECT * FROM event_url_tbl AS event
INNER JOIN artist_tbl AS artist ON event.artist_id = artist.id
ORDER BY artist.name DESC;
This cuts out a lot of the complexity/foreaches in your script. You'll end up with
Label1 (Label 1 details..) Artist1 (Artist1 details..)
Label1 (Label 1 details..) Artist2 (Artist1 details..)
Label2 (Label 2 details..) Artist3 (Artist1 details..)
Always good to bear in mind "one query is better than many". Not a concrete rule, just if it's possible to do, try to do it. Each query has overheads, and queries in loops are a warning sign.
Hopefully that helps