PHP How do I calculate level of nested calls in recursive function? - php

Question

I have a recursive function in php which gets from a database a folder tree. Each folder has an id, a name and a parent id.
function show_subfolders($parent=0, $indent=0) {
$indent++;
$folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
foreach($folders as $folder) {
echo ' '.$folder['naam'].' <br>';
show_subfolders($folder['id'], $indent);
}
}
show_subfolders();
I expect that the variable $indent tells us the level of nestedness of the recursive function, but it is not.. it just counts the number of calls. I hope it is clear that I want to know the 'generation' of each child-element.

Answer 1

Try taking the $indent var outside of the function scope, also, after you end traversing a node(folder) contents, you are going back up a level so at some point you should do a $indent--;
$indent = 0;
function show_subfolders(){
// give this function access to $indent
//you could also use a class var $this->indent if you make this into a class method
global $indent;
$folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
foreach($folders as $folder) {
echo str_repeat (' ', $indent).' '.$folder['naam'].' <br>';
$indent++;
show_subfolders($folder['id']);
$indent--;
}
}
Also added the str_repeat function so that your links are 'indented' when rendered in the browser. Although a better approach would be to draw the links in a which will allow you to control the visual indentation with css. That would make it:
$indent = 0;
function show_subfolders(){
// give this function access to $indent
//you could also use a class var $this->indent if you make this into a class method
global $indent;
$folders = sql_to_assoc("SELECT * FROM `folders` WHERE 'parent' = ".$parent.";");
if (count($folders)){
echo '<ul>';
foreach($folders as $folder) {
echo '<li> '.$folder['naam'].' </li>';
$indent++;
show_subfolders($folder['id']);
$indent--;
}
echo '</ul>';
}
}