从codeigniter中的result_array中获取特定列

I'm about using CodeIgniter for my first project. I have tried to get data from database.

$test = $this->komponen_model->get_participants_id()->result_array();
print_r($test)
Array ( 
   [0] => Array ( [id] => 1 ) 
   [1] => Array ( [id] => 4 ) 
   [2] => Array ( [id] => 7 ) 
) 

And I got this. So, I need to call each element by:

foreach ($test as $ts){
   echo $ts['id'];
}

My question is, can I make the array shorten. Just like:

Array ( 
   [0] => 1  
   [1] => 4  
   [2] => 7  
) 

I will be appreciated for anyone's advise.

Use array_column

$test = array_column($test,'id');

foreach ($test as $ts){
   echo $ts;
}