Multiple Keyword in search

PHP Code:

$keyword = explode(' ', $this->request->getVar('key'));

$builder = $this->db->table('test');
$builder->like('bio', $keyword);
$builder->orLike('first_name', $keyword);
$builder->orLike('last_name', $keyword);
$query = $builder->get();

$q = $query->getResultArray(); 


Return error:

Argument 2 passed to CodeIgniter\Database\BaseBuilder::like() must be of the type string, array given, called in