php foreach（（array）$ a-＆gt; b as $ a）return＆＃34;为foreach（）＆＃34;提供的参数无效错误

Question

要检查每个foreach()语句是否适用于数组，每个语句中的第一个参数是(array)。尽管如此，下面的代码并没有返回任何数据。

该脚本旨在根据通过$airports变量提供的数据从FAA的XML机场状态JSP文件（http://www.fly.faa.gov/flyfaa/xmlAirportStatus.jsp）中提取适用的数据。

删除每个(array)语句中的foreach()参数后，脚本将返回适用的数据，但也会返回以下警告：

Warning: Invalid argument supplied for foreach()

代码：

$xml = simplexml_load_file("http://www.fly.faa.gov/flyfaa/xmlAirportStatus.jsp");
$airports = array('ATL','AUS','BOS','DEN','LAS','LGA','LGB','JFK','OAK','PDX','PHX','RNO','SAN','SAT','SEA','SFO','SJC','SLC','SMF');
$effected = array();
$count = 0;
foreach((array) $xml->Delay_type as $Delay) {
    foreach((array) $Delay->Ground_Stop_List->Program as $Program) {
        if(in_array($Program->ARPT, $airports)) {
            $effected[] = $Program->ARPT;
            if($count == 0) {
                echo '<div class="alert">';
            }
            echo 'Departure traffic destined to <b>'.$Program->ARPT.'</b> is being held at its origin due to <b>'.$Program->Reason.'</b> until <b>'.$Program->End_Time.'</b><br />';
            $count++;
        }
    }
    foreach((array) $Delay->Ground_Delay_List->Ground_Delay as $Ground_Delay) {
        if(in_array($Ground_Delay->ARPT, $airports)) {
            $effected[] = $Ground_Delay->ARPT;
            if($count == 0) {
                echo '<div class="alert">';
            }
            /* effected[] = $Ground_Delay->ARPT; */
            echo 'Departure traffic destined to <b>'.$Ground_Delay->ARPT.'</b> is facing an average delay of <b>'.$Ground_Delay->Avg.'</b> due to <b>'.$Ground_Delay->Reason.'</b><br />';
            $count++;
        }
    }
}