How to send $_POST[var] to ssp by ajax

i have an ajax issue and hope somebody can help.
my POST Vars does not appear within the ssp file. whats wrong ?

// 1) Datatable Editor
var thisDataTable = $('table.editorTable').DataTable({
ajax:  { 
  url:  'my-ssp.php', 
  type: 'POST',
  data: {
    'pdoField' : 'webx_idn',
    'webx_idn' : 'domain.com',
  }
},


// 2) my-ssp.php
// this works!
->where('webx_idn', 'domain.com')

// doesn't work !!! a system error has occurred 
// Chrome XHR Log "Undefined index: pdoField"
->where($_POST['pdoField'], $_POST['webx_idn'])