PHP - Create array of same numbers from input array

I am trying to create an array from below array the new created array will have the same "order_number" values. For exg take csv data (source array) as $csv. Output would have like

$output_array = array (
  0 => array (
    0 => '311000000706',
    1 => 'S503053',
    2 => '1',
    3 => '123',
    4 => '1204358550',
  ),1 => 
  array (
    0 => '311000000706',
    1 => 'S503053',
    2 => '1',
    3 => '123',
    4 => '1204358550',
  ));


$input_csv = array (
  0 => 
  array (
    0 => 'order_number',
    1 => 'product_sku',
    2 => 'return_qty',
    3 => 'rma_number',
    4 => 'tracking_number',
  ),
  1 => 
  array (
    0 => '311000000706',
    1 => 'S503053',
    2 => '1',
    3 => '123',
    4 => '1204358550',
  ),
  2 => 
  array (
    0 => 'order_number',
    1 => 'product_sku',
    2 => 'return_qty',
    3 => 'rma_number',
    4 => 'tracking_number',
  ),
  3 => 
  array (
    0 => '311000000706',
    1 => 'S516135',
    2 => '1',
    3 => '123',
    4 => '1204358550',
  ),
  4 => 
  array (
    0 => 'order_number',
    1 => 'product_sku',
    2 => 'return_qty',
    3 => 'rma_number',
    4 => 'tracking_number',
  ),
  5 => 
  array (
    0 => '311000000701',
    1 => 'S526587',
    2 => '1',
    3 => '123',
    4 => '1204358550',
  ),
);

Is their any way i can create this array ? I have a tried a code but its not working well.

I want to have array of same order number with the data associated with it.