php - 无效的论点

Question

编辑：是因为 $i 被初始化为 1 而不是 0...？？？

我将从数据库中检索到的某些值存储在会话变量中。我就是这样做的：

$i = 1;   
//query to select tuples from the database;
while($i <= $num) //$num is the count of the rows returned by the query
{
    $_SESSION['first'][$i] = $row->first;
    $_SESSION['second'][$i] = $row->second;
    $i++;
}

然后我按如下方式使用它们：

$i = 1;
foreach ($_SESSION['first'] as $names)
{
    //do something with $_SESSION['second'][$i];
    $i++;
}

我得到的错误：（ 刷新页面后消失）

Invalid argument supplied for foreach() 

Answer 1

根据您的代码，$num == 0您$_SESSION将永远不会被初始化，因此$_SESSION['first']将不存在。

Answer 2

在循环之前确保变量是一个数组is_array：

$i = 1;
if (is_array($_SESSION['first'])) { foreach ($_SESSION['first'] as $names) {
    //do something with $_SESSION['second'][$i];
    $i++;
}}

问题可能来自您最初将值放入数组的方式，可以很容易地纠正is_array

$i = 1;
if (!is_array($_SESSION['first']))
    $_SESSION['first'] = array();
//query to select tuples from the database;
while($i <= $num) //$num is the count of the rows returned by the query
{
    $_SESSION['first'][$i] = $row->first;
    $_SESSION['second'][$i] = $row->second;
    $i++;
}

文档

• is_array- http://php.net/manual/en/function.is-array.php
• foreach- http://php.net/manual/en/control-structures.foreach.php