how to join table as a second level

I have a table with more then 6,000 rows that i need to "get" as join to other table. I want this join to be as "second level" of the first level. There is any way to do it? (Not with eloquent, this make it very slow...)

for example:

$query = DB::table('first_table')
->join('second_table', 'first_table.id', '=', 'second_table.first_id')
->get();

What I get from this is:

[0] => [
    [id] => 1 
    [info] => true 
    [first_id] => 1 
    [something] => 929
]
[1] => [
    [id] => 2
    [info] => true 
    [first_id] => 2
    [something] => 1212
]
[2] => [
    [id] => 3
    [info] => true 
    [first_id] => 2
    [something] => 4444
]

What I want to get is:

[0] => [
    [id] => 1 
    [info] => true 
    [second_table] => [
         [first_id] => 1 
         [something] => 929
    ]
]
[1] => [
    [id] => 2
    [info] => true 
    [second_table] => [
         [first_id] => 2 
         [something] => 1212
    ]
]
[2] => [
    [id] => 3
    [info] => true 
    [second_table] => [
         [first_id] => 2 
         [something] => 4444
    ]
]

via Chebli Mohamed