Array category subcategory - arrays

Question

I have this category and subcategory table.
The field that has the value NULL for parent_id is a category, and the ones that use parent_id are subcategories.
My tree view has subcategories assigned only to categories, so no subcategories for subcategories.
+----+---------------------+-----------+
| id | name | parent_id |
+----+---------------------+-----------+
| 1 | Laptop | NULL |
| 2 | TV | NULL |
| 3 | Tablet & Mobile | NULL |
| 4 | PC | NULL |
| 5 | Laptops | 1 |
| 6 | Laptop accessories | 1 |
| 7 | TV accessories | 2 |
If I do a SELECT * and spice it with a while I get the following array.
'category' => [
{
'name' => 'Laptop',
'id' => '1',
'parent_id' => undef
},
{
'name' => 'TV',
'id' => '2',
'parent_id' => undef
},
{
'name' => 'Table & mobile',
'id' => '3',
'parent_id' => undef
},
{
'name' => 'PC',
'id' => '4',
'parent_id' => undef
},
{
'name' => 'Laptops',
'id' => '5',
'parent_id' => '1'
},
{
'name' => 'Laptop accessories ',
'id' => '6',
'parent_id' => '1'
},
{
'name' => 'TV accessories',
'id' => '7',
'parent_id' => '2'
}
The structure I'm looking for should look like this.
category 1
-- subcategory 1.1
-- subcategory 1.2
category 2
-- subcategory 2.1
What I get now looks like
category 1
subcategory 1.1
category 2
subcategory 1.2
subcategory 2.1

Answer 1

#!/usr/bin/perl
use strict;
use warnings;
my %struct = (category => [
{
'name' => 'Laptop',
'id' => '1',
'parent_id' => undef
},
{
'name' => 'TV',
'id' => '2',
'parent_id' => undef
},
{
'name' => 'Table & mobile',
'id' => '3',
'parent_id' => undef
},
{
'name' => 'PC',
'id' => '4',
'parent_id' => undef
},
{
'name' => 'Laptops',
'id' => '5',
'parent_id' => '1'
},
{
'name' => 'Laptop accessories ',
'id' => '6',
'parent_id' => '1'
},
{
'name' => 'TV accessories',
'id' => '7',
'parent_id' => '2'
}
]);
my %tree;
for my $cat (grep ! defined $_->{parent_id}, #{ $struct{category} }) {
$tree{ $cat->{id} } = $cat;
}
for my $cat (grep defined $_->{parent_id}, #{ $struct{category} }) {
$tree{ $cat->{parent_id} }{subcat}{ $cat->{id} } = $cat;
}
use Data::Dumper; print Dumper \%tree;