<?php
$options = array (
                  "1567" => "test",
                  "1853" => "test1",
                  );


$option = array (
"none" => "N/A"
);

$final = array_merge($option,$options);
var_dump($final);

$finalNew = $option + $options ;
var_dump($finalNew);

?>

array(3) {
  ["none"]=>
  string(3) "N/A"
  [0]=>
  string(4) "test"
  [1]=>
  string(5) "test1"
}
array(3) {
  ["none"]=>
  string(3) "N/A"
  [1567]=>
  string(4) "test"
  [1853]=>
  string(5) "test1"
}