javascript - 尝试获取非对象的属性 -> 如何检查对象是否存在

Question

在使用 Dom Document 时如何检查对象是否存在，因为我正在获取

error "Trying to get property of non-object"

$getplacename            = '//table//tr';
$getplacename2           = $xpath->query($getplacename);
//loop through each individual card
foreach($getplacename2 as $getplacename22) {

echo  $getplacename22 ->childNodes->item(0)->childNodes->item(2)->textContent;
echo  $getplacename22 ->childNodes->item(4)->textContent;
echo "<br /><br /><br />";
}

Answer 1

嗯，我认为执行此类操作的最简单方法是将代码更改为类似的内容(假设错误发生在以下行之一中):

foreach($getplacename2 as $getplacename22) {
    if ($getplacename22->childNodes->item(0) != null && $getplacename22->childNodes->item(0)->childNodes->item(2) != null) {
        echo $getplacename22->childNodes->item(0)->childNodes->item(2)->textContent;
    }
    if($getplacename22 ->childNodes->item(4) != null) {
        echo $getplacename22->childNodes->item(4)->textContent;
    }
    echo "<br /><br /><br />";
}