将分钟向下舍入到最接近的 7.小时

$seconds = time();
$rounded_seconds = round($seconds / (15 * 60)) * (15 * 60);

echo "Original: " . date('H:i', $seconds) . "\n";
echo "Rounded: " . date('H:i', $rounded_seconds) . "\n";

此示例获取当前时间并将其舍入到最接近的四分之一，并打印原始时间和舍入时间。

PS：如果要将其四舍五入，请替换为.round()floor()

您的全部功能将是这样的...

function roundToQuarterHour($timestring) {
    $minutes = date('i', strtotime($timestring));
    return $minutes - ($minutes % 15);
}