Convert comma separated string to array and test for entries

  $PermittedCountryCodes = "FR,GB";
  $PermittedCountryCodes = trim($PermittedCountryCodes);
  $PermittedCountryCodes = strtoupper($PermittedCountryCodes);
  $PermittedCountryCodes = explode(',', $PermittedCountryCodes);        //Convert to array
  $PermittedCountryCodes = array_map('trim', $PermittedCountryCodes);   //Trim each array entry
  if (array_search("GB", $PermittedCountryCodes) !== False)
  {
    //'GB' IS PRESENT
    
  }

Convert array into comma separated string

  $Types = array();
  if (something)
    $types[] = "SMS";
  if (somethingelse)
    $Types[] = "TEL";
  $Types = implode(',', $Types);      //Convert array to comma seperated string