Create an HTML calendar with PHP and Carbon

calendar.php

<?php
// Make sure Carbon is available

function renderCalendar($dt) {
    // Make sure to start at the beginnen of the month
    $dt->startOfMonth();
    
    // Set the headings (weeknumber + weekdays)
    $headings = ['Weeknumber', 'Mondag', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saterday', 'Sunday'];

    // Create the table
    $calendar = '<table class="calendar">';
    $calendar .= '<caption>'.$dt->format('F Y').'</caption>';
    $calendar .= '<tr>';

    // Create the calendar headings
    foreach ($headings as $heading) {
        $calendar .= '<th class="header">'.$heading.'</th>';
    }

    // Create the rest of the calendar and insert the weeknumber
    $calendar .= '</tr><tr>';
    $calendar .= '<td>'.$dt->weekOfYear.'</td>';

    // 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>';
            $calendar .= '<td>'.$dt->weekOfYear.'</td>';
        }
        // Append the column
        $calendar .= '<td class="day" rel="'.$dt->format('Y-m-d').'">'.$dt->day.'</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;
}

$dt = Carbon::createFromDate(2018, 05, 01);

echo renderCalendar($dt);

Good job.

I tried this code for my project, thanks..
Although for a Month where the last day is Sunday, this code add unused td at the end of calendar..
So I add an if at:

// Increment the date with one day
$dt->addDay();

With:
if($dt->day != $daysInMonth) {
$dt->addDay();
}