How can i fix the output of this recursion function - php

Question

function my_recurse($id,$tree=array())
{
$hols = array();
$overall = array();
$asd = $this->db->get_where('story', array('story_id'=>$id))->row_array();
if(isset($asd['story_id'])){
$preds = explode(',',$asd['story_pred']);
if($preds[0] != 0)
{
$hols[] = $preds[0];
$hols = array_merge($tree, $hols);
$this->my_recurse($preds[0],$hols);
}
}
print_r($hols);
}
say for example i have this tree
story1 NULL
story2 story1
story3 story2
story4 story3
and when i enter story4 as my id in the function it always returns the story3 and not story1,story2 and story3. dont know why it reverses the output after the recursion happens. any suggestions would be appreciated

Answer 1

It's hard to say if this will be easy or possible without knowing your database structure, but you don't need recursion to find the path of a tree node to the root - you can do this with a self join. Also, you should avoid making a query in a recursive function. If you can describe your table structure I can attempt to show you how to get a result set that is the tree path in order.

Answer 2

The problem with your code is that its passing the current preds up to the parent hence the reverse tree. Instead it should be getting the preds from the parent
This should work if I understood your requirements clearly
<?php
function my_recurse($id) {
$hols = array();
$overall = array();
$asd = getFromDB($id);
if(isset($asd['story_id'])){
$preds = explode(',',$asd['story_pred']);
if($preds[0] != 0) {
$hols[] = $preds[0];
$hols = array_merge(my_recurse($preds[0]), $hols);
} else {
return $hols;
}
print "preds of {$id} : ";
print implode(', ', $hols) . "\n";
return $hols;
}
}
function getFromDB($id) {
$data = array(1 => array('story_id'=>1, 'story_pred' => '0'),
2 => array('story_id'=>2, 'story_pred' => '1'),
3 => array('story_id'=>3, 'story_pred' => '2'),
4 => array('story_id'=>4, 'story_pred' => '3'),
);
return $data[$id];
}
my_recurse(4);
Running the script above..
$ /usr/bin/php recurse.php
preds of 2 : 1
preds of 3 : 1, 2
preds of 4 : 1, 2, 3
PS: Please add your sample input, output and expected output. It took me 15 minutes to try understanding your problem.