PHP SimpleXML：优雅处理XML中可选时间字段并显示“全天”事件

<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>

<?php

// 假设XML数据已存储在一个字符串或文件中
// 为演示方便，我们直接构建一个SimpleXMLElement对象
$xmlString = <<<XML
<events>
    <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>
    <event>
        <startdate>25/11/2021</startdate>
        <alldayevent>true</alldayevent>
        <description>Event 3 (Another Day)</description>
        <category>Meetings</category>
    </event>
    <event>
        <startdate>25/11/2021</startdate>
        <alldayevent>false</alldayevent>
        <starttime>09:00</starttime>
        <endtime>10:00</endtime>
        <description>Event 4 (Another Day)</description>
        <category>Workshops</category>
    </event>
</events>
XML;

// 实际应用中，通常从文件加载：
// $sxml = simplexml_load_file($url) or die("Error: Cannot create object");
$sxml = simplexml_load_string($xmlString) or die("Error: Cannot create object from string");


echo '<div class="calendar">';

// 搜索所有事件的开始日期
$starts = $sxml->xpath('//event/startdate');

// 获取这些事件的唯一开始日期
$dates = array_unique(array_map('strval', $starts)); // 使用strval确保日期作为字符串进行比较

foreach($dates as $date) {    
    echo "<li><h1>{$date}</h1></li>" ."\n";

    // 搜索在每个开始日期发生的所有事件
    $expression = "//event[startdate='{$date}']"; // 更精确的XPath，直接定位到event
    $events = $sxml->xpath($expression);

    // 遍历这些事件并找到它们的描述和时间
    foreach ($events as $event){
        // 获取alldayevent标志
        $alldayEventNodes = $event->xpath('./alldayevent');
        $isAllDay = !empty($alldayEventNodes) && ((string)$alldayEventNodes[0] === "true");

        echo "\t" , "<li>";
        echo "<div class='time'>";

        if ($isAllDay) {
            echo "All Day";
        } else {
            // 获取starttime和endtime。这里假设如果不是全天事件，这两个字段必然存在。
            // 实际中如果这两个字段也可能缺失，需要进一步的空值检查。
            $startTimeNodes = $event->xpath('./starttime');
            $endTimeNodes = $event->xpath('./endtime');

            $st = !empty($startTimeNodes) ? (string)$startTimeNodes[0] : 'N/A';
            $et = !empty($endTimeNodes) ? (string)$endTimeNodes[0] : 'N/A';

            echo "{$st} - {$et}";
        }

        echo "</div>"; // End .time div

        // 获取描述和类别
        $descriptionNodes = $event->xpath('./description');
        $categoryNodes = $event->xpath('./category');

        $description = !empty($descriptionNodes) ? (string)$descriptionNodes[0] : 'No Description';
        $category = !empty($categoryNodes) ? (string)$categoryNodes[0] : 'No Category';

        echo "<div class='event'><b> {$description}</b>  //  {$category}</div>";
        echo "</li>";
        echo "\n";
    }
    echo "\n";
}
echo "</div>";

?>

<div class="calendar"><li><h1>24/11/2021</h1></li>
    <li><div class='time'>All Day</div><div class='event'><b> Event 1</b>  //  Main Events</div></li>
    <li><div class='time'>14:00 - 16:30</div><div class='event'><b> Event 2</b>  //  Main Events</div></li>

<li><h1>25/11/2021</h1></li>
    <li><div class='time'>All Day</div><div class='event'><b> Event 3 (Another Day)</b>  //  Meetings</div></li>
    <li><div class='time'>09:00 - 10:00</div><div class='event'><b> Event 4 (Another Day)</b>  //  Workshops</div></li>

</div>