What potential issues or complications could arise from implementing an automatic reminder email system without using a cronjob in PHP?

One potential issue is that without using a cronjob, the reminder emails may not be sent at the intended times due to the reliance on user activity to trigger them. To solve this, you can implement a system that checks for pending reminders at regular intervals and sends them accordingly. 

// Check for pending reminders every hour
$current_time = time();
$reminder_interval = 3600; // 1 hour

// Query database for reminders that are due
$reminders = $db->query("SELECT * FROM reminders WHERE reminder_time <= $current_time");

foreach($reminders as $reminder) {
    // Send reminder email
    mail($reminder['email'], 'Reminder', $reminder['message']);

    // Update reminder status
    $db->query("UPDATE reminders SET status = 'sent' WHERE id = " . $reminder['id']);
}

Keywords

PHP automatic reminder email system cronjob scheduling time-based tasks

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