Sorting data in php/mysql - php

Question

so i have a question regarding, hmmm filtering data in mysql/php.
So i have table lets say
ID | fk1 | fk2
1 1 1
2 1 2
3 1 3
4 2 1
5 2 2
6 3 3
Basicaly i have in same table many occurancies of fk1 that are referenced to fk2 and when i output that in table ofcourse i get result as
1 1
1 2
1 3
2 1
etc. And that is normal. What i want to do is basically output one time FK2 value lets say 1, and all corresponding FK1 values below it. Sorta like group by but for each occurancie of FK2 i need all the FK1s that have that FK2 in their row.
I managed to get it working somehow so that all FK1 print out and corresponding FK2 but other way around wont work :S
$FK1 = '';
while($row = mysql_fetch_array($result_set)){
if($FK1 != $row['fk1']){
if($FK1 != ''){
echo $printout;
}
$FK1 = $row['fk1'];
$printout = "<tr class='success'><td>" . "<strong>" . $row['fk1']. "</td></tr>";
}
$printout = $printout .'<td class="warning"> '.$row['fk2']. '</td></tr>';
}
echo $printout ;
Any idea how to do this with some smart loop instead of using multiple queries on base?
Thanks

Answer 1

For each iteration of the loop that prints the query, you can check if the previous iteration printed the same thing and (if yes) skip the printing or print the current one if not.
I hope I understood the question and my answer is clear enough.
Something like this:
$cFk1 = "";
foreach($query_result as $cVal){
if($cVal != cFk1){
print $cVal;
}
$cFk1 = $cVal;
}

Answer 2

You can try GROUP_CONCAT in your query such as:
SELECT
fk2, GROUP_CONCAT(fk1) fk1,
FROM
table
GROUP BY
fk2
And then in your PHP code:
foreach($rows as $row) {
// plain echo
echo $row['fk2'].' '.$row['fk1'];
}
or
foreach($rows as $row) {
// or with post-processing
echo $row['fk2'].' ';
$fk1 = explode(',', $row['fk1']);
foreach($fk1 as $value) {
echo $value.'-';
}
}
But beware - GROUP_CONCAT has its limits, you should make sure the strings don't contain the separator (if it's only numbers, it's ok), etc.