Create an HTML calendar with PHP and Carbon

Calendar_Function.php

<?php
public static function Render()
{
    #Sets Current Date
    $dt = Carbon::createFromFormat('Y,m,d', Date('Y,m,d'));

    // Make sure to start at the beginning of the month
    $dt->startOfMonth();

    // Set the headings (weeknumber + weekdays)
    $headings = [ 'M', 'T', 'W', 'T', 'F', 'S', 'S']; #translation enhancement
    // Create the table
    $calendar = '<table class="calendar" id="wp-calendar">';
    $calendar .= '<caption>'.$dt->format('F Y').'</caption>';
    $calendar .= '<tr>';
    // Create the calendar headings
    foreach ($headings as $heading)
    {
        $calendar .= '<th class="header">'.$heading.'</th>';
    }

    // Day of week isn't monday, add empty preceding column(s)
    if ($dt->format('N') != 1)
    {
        $calendar .= '<td colspan="'.($dt->format('N') - 1).'">&nbsp;</td>';
    }
    // Get the total days in month
    $daysInMonth = $dt->daysInMonth;
    // Go over each day in the month
    for ($i = 1; $i <= $daysInMonth; $i++)
    {
        // Monday has been reached, start a new row
        if ($dt->format('N') == 1)
        {
            $calendar .= '</tr><tr>';
        }
        // Append the column
        $calendar .= '<td class="day" rel="'.$dt->format('Y-m-d').'">';
        if ($dt->day == Carbon::now()->format('d') )
        {
            #Active Date Today
            $calendar .= "<a>" . $dt->day . '</a>';
        }
        else
        {
            #Not Active Dates
            $calendar .= $dt->day;
        }

        $calendar .= '</td>'; // Increment the date with one day

        $dt->addDay();
    }
    // Last date isn't sunday, append empty column(s)
    if ($dt->format('N') != 7)
    {
        $calendar .= '<td colspan="'.(8 - $dt->format('N')).'">&nbsp;</td>';
    }
    // Close table
    $calendar .= '</tr>';
    $calendar .= '</table>';
    // Return calendar html
    return $calendar;
}

echo MyClass::Render();