PHP Dynamically Creating Nested Elements

Question

I am creating an array from a query using various tables that gives me a variable number of parents each containing a variable number of values.

For simplicity, say I have the following (using p as parent and v as value):

$parent[0] = array("p1v1","p1v2");  
$parent[1] = array("p2v1","p2v2","p2v3");  
$parent[2] = array("p3v1","p3v2");

I need to created the following tree:

p1v1
- p2v1
  - p3v1
  - p3v2
- p2v2
  - p3v1
  - p3v2
- p2v3
  - p3v1
  - p3v2
p1v2
- p2v1
  - p3v1
  - p3v2
- p2v2
  - p3v1
  - p3v2
- p2v3
  - p3v1
  - p3v2

Nested foreach loops:

foreach ($parent[0] as $key1 => $value1) {
    echo $value1 . '<br />';
    foreach ($parent[1] as $key2 => $value2) {
        echo '-- ' . $value2 . '<br />';
        foreach ($parent[2] as $key3 => $value3) {
            echo '---- ' . $value3 . '<br />';
        }
    }
}

I can do this with nested foreach loops as above but my problem is that I don't know how many parents I will have for a given query. So, how can I create a variable number of nested foreach loops... I am sure there is a better way.

Thanks for any input/advice.

That's what recursion is for.

Roy
– Roy

2014-07-19 18:38:14 +00:00
Commented Jul 19, 2014 at 18:38 — Roy
– Roy, Commented Jul 19, 2014 at 18:38

FuzzyTree · Accepted Answer · 2014-07-19 18:37:32Z

3

$parent[0] = array("p1v1","p1v2");  
$parent[1] = array("p2v1","p2v2","p2v3");  
$parent[2] = array("p3v1","p3v2");

function print_nested_array($parent,$level=0) {
    foreach($parent[$level] as $value) {        
        if($level > 0) {
            foreach(range(0,$level-1) as $j) {
                echo '--';
            }

            echo ' ';
        }            

        echo $value . "\n"; //change to "<br>" for html

        if($level < count($parent)-1)
            print_nested_array($parent,($level+1));
    }
}

print_nested_array($parent,0);

Demo

answered Jul 19, 2014 at 18:37

FuzzyTree

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