PHP中将日期时间转换为ISO 8601 UTC格式的指南

<?php
$dateString = "Fri, 15 Mar 2019 08:56:57 +0000";
try {
    $dateTime = new DateTime($dateString);
    echo "原始日期时间对象创建成功。\n";
} catch (Exception $e) {
    echo "日期时间解析错误: " . $e->getMessage() . "\n";
    exit();
}
?>

<?php
$dateString = "Fri, 15 Mar 2019 08:56:57 +0000";
$dateTime = new DateTime($dateString);

// 使用 \DateTime::ISO8601 格式化
$iso8601_format1 = $dateTime->format(\DateTime::ISO8601);
echo "ISO 8601 (常量): " . $iso8601_format1 . "\n"; // 输出: 2019-03-15T08:56:57+0000

// 使用 "c" 格式化
$iso8601_format2 = $dateTime->format("c");
echo "ISO 8601 (字符 'c'): " . $iso8601_format2 . "\n"; // 输出: 2019-03-15T08:56:57+00:00
?>

<?php
// 示例1: 原始日期时间已在UTC
$dateStringUTC = "Fri, 15 Mar 2019 08:56:57 +0000";
$dateTimeUTC = new DateTime($dateStringUTC);
$dateTimeUTC->setTimezone(new DateTimeZone("UTC"));
$outputUTC = $dateTimeUTC->format(\DateTime::ISO8601);
echo "原始UTC日期转换为UTC: " . $outputUTC . "\n"; // 输出: 2019-03-15T08:56:57+0000

// 示例2: 原始日期时间不在UTC
$dateStringNonUTC = "Fri, 15 Mar 2019 08:56:57 +0230"; // 带有+0230偏移
$dateTimeNonUTC = new DateTime($dateStringNonUTC);
echo "原始非UTC日期: " . $dateTimeNonUTC->format(\DateTime::ISO8601) . "\n"; // 输出: 2019-03-15T08:56:57+0230

$dateTimeNonUTC->setTimezone(new DateTimeZone("UTC"));
$outputNonUTC = $dateTimeNonUTC->format(\DateTime::ISO8601);
echo "非UTC日期转换为UTC: " . $outputNonUTC . "\n"; // 输出: 2019-03-15T06:26:57+0000
?>

<?php
function convertToIso8601Utc(string $dateString): string
{
    try {
        // 1. 解析日期字符串为 DateTime 对象
        $dateTime = new DateTime($dateString);

        // 2. 将 DateTime 对象设置为 UTC 时区
        $dateTime->setTimezone(new DateTimeZone("UTC"));

        // 3. 格式化为 ISO 8601 字符串 (推荐使用 "c" 格式)
        return $dateTime->format("c");

    } catch (Exception $e) {
        // 捕获解析或时区设置错误
        error_log("日期时间转换失败: " . $e->getMessage() . " 原始字符串: " . $dateString);
        // 根据实际需求返回默认值或抛出异常
        return ''; 
    }
}

// 测试用例
echo "示例1 (已是UTC): " . convertToIso8601Utc("Fri, 15 Mar 2019 08:56:57 +0000") . "\n";
echo "示例2 (带偏移): " . convertToIso8601Utc("2023-10-27 14:30:00 +0800") . "\n";
echo "示例3 (不带偏移，默认服务器时区): " . convertToIso8601Utc("2023-10-27 14:30:00") . "\n"; // 假设服务器时区为+0800
echo "示例4 (无效日期): " . convertToIso8601Utc("Invalid Date String") . "\n";
?>