如何随意爆炸元素？

This is my code:

function get_random(){
    $filter_word     = '1,2,3,4,5,6,7,8,9';
    $array = explode(',', $filter_word);
    $randomKeys = array_rand($array, 2);
    $str = '';
    foreach($randomKeys as $key){
        $str = $array[$key];
    }

    return $str;
}

The problem that if I used array_rand i must know the number of elements to can add the number in array_rand and I can't know something like this (it's a data stored into the database) so if the elements are less than two it gives me an error:

Warning: array_rand(): Second argument has to be between 1 and the number of elements in the array

Is there a better way to make this?

you can use count() before using array_rand-

function get_random(){
    $filter_word     = '1,2,3,4,5,6,7,8,9';
    $array = explode(',', $filter_word);
    $str = '';
    if(count($array)>1){
       $randomKeys = array_rand($array, 2);

       foreach($randomKeys as $key){
           $str = $array[$key];
       }
    }
    else{
            $str = $filter_word;
     }
    return $str;
  }

I suppose you are looking for something like this:

$randCount = rand(1, count($array));
$randomKeys = array_rand($array, $randCount);