Nested SQL resulting to Nested List - php

Question

Any ideas on how can I generate a nested list without the need to recreate a lot of select statements?
I'm currently using this code
<ol>
<?php
$getparents=mysql_query("select id,subject from list");
while($parent=mysql_fetch_assoc($getparents)){
?>
<li><?php echo $parent["id"];?></li>
<?php
$childsparent=$parent["id"];
$getchild=mysql_query("select id,subject from list where parent_id='".$childsparent."'");
if (!mysql_num_rows($getchild){
echo '</ol>';
}
else
{
echo '<ol>';
while ($child=mysql_fetch_assoc($getchild)){
echo '<li>'.$child["subject"].'</li>';
}
$childsparent=$child["id"];
}
?>
</ol>
Is there a way to stop the while from getting all results and check a result first if it has child nests before it moves forward?
The result should be something like
1.
2.
2.1
2.1.1
2.2
3

Answer 1

I found this function I wrote some time ago. I think it is the kind of thing you want. You just need to change the logic to print out rather than store to an array:
function nestify( $arrs, $depth_key = 'depth' )
{
$nested = array();
$depths = array();
foreach( $arrs as $key => $arr ) {
if( $arr[$depth_key] == 0 ) {
$nested[$key] = $arr;
$depths[$arr[$depth_key] + 1] = $key;
}
else {
$parent =& $nested;
for( $i = 1; $i <= ( $arr[$depth_key] ); $i++ ) {
$parent =& $parent[$depths[$i]];
}
$parent[$key] = $arr;
$depths[$arr[$depth_key] + 1] = $key;
}
}
return $nested;
}
$arr = array(
array( 'name' => 'Joe Splogs', 'depth' => 0 ),
array( 'name' => 'ProSplogger', 'depth' => 0 ),
array( 'name' => 'Pinky Lyres', 'depth' => 1 ),
array( 'name' => 'Pseudologia fantastica', 'depth' => 2 ),
array( 'name' => 'TextLinkBarry', 'depth' => 1 ),
array( 'name' => 'Foo bar Jones', 'depth' => 0 )
);
$new = nestify( $arr, 'depth' );
#-> Returns
array (
'0' => array
(
'name' => 'Joe Splogs',
'depth' => 0
),
'1' => array
(
'name' => 'ProSplogger',
'depth' => 0
'2' => array
(
'name' => 'Pinky Lyres',
'depth' => 1
'3' => array
(
'name' => 'Pseudologia fantastica',
'depth' => 2
),
),
'4' => array
(
'name' => 'TextLinkBarry',
'depth' => 1
),
),
'5' => array
(
'name' => 'Foo bar Jones',
'depth' => 0
),
);