joomla组件中的错误

我正在尝试创建一个joomla组件。该组件是关于生成一个句子的。基本上，这是帮助我生成它的代码/函数

function getCategory()
{
    $cat = array("walk","reside","eat");
    return $b = $cat[array_rand($cat)];
}
function getS1() //function 1.1
{
      $db = JFactory::getDBO();
      $query = "select words from #__wordbank where function = 1.1 order by rand() LIMIT 1";
      $db->setQuery($query);
      return $db->loadResult();
}
function getV11() //function 2.11
{
    $db = JFactory::getDBO();
    $b = getCategory();
    $query = "select words from #__wordbank where function = 2.11 AND category = '$b' order by rand() LIMIT 1";
    $db->setQuery($query);
    return $db->loadResult();
}
function getP1() //function p1.1
{
    //load preposition
    $db = JFactory::getDBO();
$b = getCategory();
    $query = "select words from #__wordbank where function = 'p1.1' AND category =   '$b' order by rand() LIMIT 1";
    $db->setQuery($query);
    return $db->loadResult();
}
function getP2() //function p1.2
{
    //load noun 
    $db = JFactory::getDBO();
    $b = getCategory();
    $query = "select words from #__wordbank where function = 'p1.2' AND category = '$b' order by RAND() limit 1";
    $db->setQuery($query);
    return $db->loadResult();
}

问题是当i getCategory()时，返回值总是不同的。我尝试使用if else，但由于$cat[array_rand($cat)]，它仍然返回不同的值。如果你们能帮我解决这个错误，我将不胜感激。