PHP: how to save result of recursive function in array?

Question

I have changed version of this recursive function... http://www.phpbuilder.com/articles/databases/mysql/handling-hierarchical-data-in-mysql-and-php.html

What I need is a way to save the returned value of this function in an array so that I can reverse the order of array elements. The function works well for me, but I need a way to save values. Here is the code...

function display_children($category_id, $level) {
 global $database;
 $result = mysql_query("SELECT * FROM parents WHERE id_roditelja='$category_id'") or die(mysql_error());
 $niz = array();
 while ($row = mysql_fetch_array($result)) {
 echo str_repeat(' ', $level) . $row['naziv'] . "<br/>";
 array_push($niz, display_children($row['parent_id'], $level + 1));
//this is one way I tried, and I get $niz with exact number of elements but each is null
//in this $niz array I need to store values of recursion
 var_dump($niz);
 }
}

• Ivan Yonkov: chould you dump $niz outside the while, your null problem is probably because of the second parameter given to array_push. Your recursive function does not return any value to be send to array_push, I mean you have lots of operation, but no value at the end
• Christoph Diegelmann: @som: can you explain why this is not a recursive function ? It calls itself ? Thug: you forgot return $niz; after your while
• som: Sorry I don't see properly.

Answer 1

I think you want this:

function display_children/* <- this must be the same */($category_id, $level) {
 global $database;
 $result = mysql_query("SELECT * FROM parents WHERE id_roditelja='$category_id'") or die(mysql_error());
 $niz = array();
 while ($row = mysql_fetch_array($result)) {
 $niz[] = str_repeat(' ', $level) . $row['naziv'] . "<br/>"; // we need to save this
 $niz = array_merge($niz, /* as this -> */display_children($row['parent_id'], $level + 1)); // array_merge doesn't take a reference so we need to store its result in $niz
 }
 return $niz;
}

if you want a tree like structure use array_push instead of array_merge. As noone seems to notice: His function can't return anything without a return statement !

• Ivan Yonkov: As maybe we have already noticed that, but in comments, because one more row, does not deserve a whole answer :)
• Thug: Same result as my way...null again. My function returns names of products, as it should, but i need it saved in array, because order of elements in not the right.
• Christoph Diegelmann: @Thug your function (how you posted it) may display something but it won't return anything because it lacks a return statement ! Can you post how you call your function and an example output ?
• Thug: This is example od output Zaštita za zube Borilački aksesoari Borilački sportovi Sportska oprema array 0 => null array 0 => null array 0 => null array 0 => null
• Thug: i call function like display_chield(58,4)