简化:mysqli num_rows不起作用

Question

如何使用mysqli输出返回的行数？下面的代码显示0虽然是while循环(而$ s-> fetch()echo $ uid;)显示2个结果;

$m = new mysqli(MYSQL_SERVER, MYSQL_USER, MYSQL_PASS, MYSQL_DB);
$s=$m->prepare("SELECT uid FROM user WHERE token=? AND secret=?");
$s->bind_param('ss',$rt, $rs);
$rt='c';
$rs='d';
$s->execute();
$s->bind_result($uid);
$s->fetch();
print_r($s->num_rows); // RESULTS IN 0

Answer 1

你必须在fetch mysqli_stmt::store_result()之后mysqli_stmt::execute()和之前打电话才能知道mysqli_stmt::num_rows:

$s->execute();
$s->store_result();
print_r($s->num_rows);

PHP文档 num_rows

PHP文档 store_result()