<?php
$values = [
'orderperson',
'address',
'postnumber',
'city',
'phone',
'email'
];

$shipvalues = [
'recipient',
'address1',
'postnumber1',
'city1',
'phone1',
'email1'
];

foreach($values as $value) {
 if(empty($_POST[$value])) {
  header("Location: http://example.com?errors=true");
 }
}

if (array_key_exists("checkbox", $_POST) && !empty($_POST['checkbox'])) {
  foreach ($shipvalues as $shipvalue) {
    if(empty($_POST[$shipvalue])) {
     header("Location: http://example.com?errors=true");
    }
   }
 }

header("Location: http://example.com");
exit;