以下是代码

$this->sth = $this->pdo->prepare($sql); $this->sth->execute(array_values(array_merge($vals, $wheres))); return $this->sth->rowCount();

prepare的sql语句

update fb_articles set view_num = ? where id = ?

execute的数组

array(2) { [0]=> string(12) "view_num + 1" [1]=> string(2) "19" }

return 是0
如果将sql语句直接拼接执行是可以的，那么在pdo中要怎么使用呢