laravel如何打印orm封装的sql语句

$query = CdbForumSellthreadSearch::where($params)->orderBy("$orderby", "$ascDesc")->offset($start)->limit($limit);
$list = CdbForumSellthreadSearch::where($params)->orderBy("$orderby", "$ascDesc")->offset($start)->limit($limit)->get()->toArray();

//打印出的sql是预编译的sql语句，带有问号占位符的sql 

print_r($query->toSql());

//下面打印出占位符对应的变量的值，数组里面的顺序和占位符的顺序是一致的

echo '<pre>';

print_r($query->getBindings());

exit;