由于缺少时间而导致的PHP SimpleXML错误

Question

我有下面的代码，它显示了一个日历XML提要，但是，并不是所有事件都有开始/结束时间。这会导致一个错误。当一个事件没有开始和结束时间时，我希望它显示"全天"。

//load xml file
$sxml = simplexml_load_file($url) or die("Error: Cannot create object");
echo '<div class="calendar">';
#search for all event start dates
$starts = $sxml->xpath('//event/startdate');
#get the unique start dates of these event
$dates = array_unique($starts);

foreach($dates as $date) {    
echo "<li><h1>{$date}</h1></li>" ."n";
#search for all events taking place on each start date
$expression = "//event/startdate[.='{$date}']";
$events = $sxml->xpath($expression);
#iterate through these events and find their description
foreach ($events as $event){
echo "t" , "<li><div class='time'>{$event->xpath('./following-sibling::starttime')[0]} - {$event->xpath('./following-sibling::endtime')[0]}</div><div class='event'><b> {$event->xpath('./following-sibling::description')[0]}</b>  //  {$event->xpath('./following-sibling::category')[0]}</div></li>";
echo "n";
}
echo "n";
}
echo "</div>";

下面的示例XML文件：

<event>
<startdate>24/11/2021</startdate>
<alldayevent>true</alldayevent>
<description>Event 1</description>
<category>Main Events</category>
</event>
<event>
<startdate>24/11/2021</startdate>
<alldayevent>false</alldayevent>
<starttime>14:00</starttime>
<endtime>16:30</endtime>
<description>Event 2</description>
<category>Main Events</category>
</event>

预期输出：

如果事件的时间/alldayevent=true，则显示开始和结束时间，否则如果alldayevent=true，则输出"全天">

Answer 1

我相信，如果我正确理解你的话，你正在寻找以下内容。

像这样更改foreach：

foreach($dates as $date) {     
echo "<li><h1>{$date}</h1></li>" ."n";
$expression = "//event/startdate[.='{$date}']";
$events = $sxml->xpath($expression) ;
foreach ($events as $event){
echo $event->xpath('.//following-sibling::description')[0]."n";
if (($event->xpath('.//following-sibling::alldayevent'))[0] == "true") {
echo "t" , "<li><div class='time'>All Day</div></li>" ."n";
} else {
$st = $event->xpath('.//following-sibling::starttime')[0];
$et = $event->xpath('.//following-sibling::endtime')[0];
echo "t" , "<li><div class='starttime'>$st</div></li>" ."n";
echo "t" , "<li><div class='endtime'>$et</div></li>" ."n";

}
}
}

输出：

<li><h1>24/11/2021</h1></li>
Event 1
<li><div class='time'>All Day</div></li>
Event 2
<li><div class='starttime'>14:00</div></li>
<li><div class='endtime'>16:30</div></li>