Chat Logger

<?php
date_default_timezone_set('Europe/Sofia');
$currentDate = create_time_from_date_string($_GET['currentDate']);
$messages = explode("\n", $_GET['messages']);

$messagesList = array();
$mostRecentTime = 0;
foreach ($messages as $message) {
    $startDateStr = strrpos($message, '/') + 1;
    $messageStr = trim(substr($message, 0, $startDateStr - 2));
    $dateStr = trim(substr($message, $startDateStr, strlen($message) - $startDateStr));
    $timeKey = create_time_from_date_string($dateStr);
    if ($timeKey > $mostRecentTime) {
        $mostRecentTime = $timeKey;
    }
    $messagesList[$timeKey] = $messageStr;
}

ksort($messagesList);
foreach ($messagesList as $message) {
    echo '<div>' . htmlspecialchars($message) . "</div>\n";
}

$timespan = $currentDate - $mostRecentTime;
$currentDate = date('d-m-Y', $currentDate);
$mostRecentDate = date('d-m-Y', $mostRecentTime);
$daysDiff = ((int)substr($currentDate, 0, 2)) - ((int)substr($mostRecentDate, 0, 2));
echo '<p>Last active: <time>';
if ($daysDiff > 1) {
    echo $mostRecentDate . '</time></p>';
} elseif ($daysDiff == 1) {
    echo 'yesterday</time></p>';
} else {
    if ($timespan >= 3600) {
        $timespan = (int)($timespan / 3600);
        echo $timespan . ' hour(s) ago</time></p>';
    } elseif ($timespan >= 60) {
        $timespan = (int)($timespan / 60);
        echo $timespan . ' minute(s) ago</time></p>';
    } else {
        echo 'a few moments ago</time></p>';
    }
}

function create_time_from_date_string($dateStr) {
    $dateArr = preg_split('/\D+/', $dateStr, -1, PREG_SPLIT_NO_EMPTY);
    if (count($dateArr) == 6) {
        return mktime($dateArr[3], $dateArr[4], $dateArr[5], $dateArr[1], $dateArr[0], $dateArr[2]);
    }

    return null;
}