A PHP Error was encountered

Severity: Warning
Message: Undefined variable $str_header_kop
Filename: views/page.php
Line: 2

TRACE [0]array(2) {
  [0]=>
  array(2) {
    ["file"]=>
    string(43) "sys/codeigniter/core/CodeIgniter.php at 533"
    ["class->method"]=>
    string(16) "Main->index()"
  }
  [1]=>
  array(3) {
    ["file"]=>
    string(60) "mediationmiddeninhetland.nl/httpdocs/public/index.php at 460"
    ["args"]=>
    array(1) {
      [0]=>
      string(89) "/var/www/vhosts/mediationmiddeninhetland.nl/httpdocs/sys/codeigniter/core/CodeIgniter.php"
    }
    ["function"]=>
    string(12) "require_once"
  }
}