Frame the genitive of a name

Genitive

function genitive($name) {
  $suffix = 's';
  $name = trim($name);
  
  if('ce' == substr($name, -2)) {
    $suffix = '’';
  }
  
  elseif (in_array(substr($name, -1), array('s', 'ß', 'x', 'z'))) {
    $suffix = '’';
  }
  
  return $name.$suffix; 
}