Date validation via dropdown - php

Question

We all know that <input type="date"> is not ideal for forms that require a future date to be selected.
My idea was to create a drop-down that only lists off the current date and every date for the rest of the year.
<select>
<option value="Not Selected" disabled selected>Please select a date.</option>
<optgroup label="September">
<option value="1st">Sunday 1st</option>
<option value="etc">Rest of month</option>
<optgroup label="October">
<option value="1st">Tuesday 1st</option>
<option value="etc">Rest of month</option>
<optgroup label="November">
<option value="1st">Friday 1st</option>
<option value="etc">Rest of month</option>
<optgroup label="December">
<option value="1st">Sunday 1st</option>
<option value="etc">Rest of month</option>
</select>
This would allow me to have more control over the user input without needing to validate for a future date. Of course I could use something like php echo date for the current one but the requirements would be;
1) Get current month and add to <optgroup label="[MONTH]">
2) Get current date
3) Calculate dates remaining and then echo them into their own 'DD/MM/YYYY`
I don't want to have to remove the previous day's date on a daily basis and I'm not too sure how to go about generating this but I've seen date drop-downs on sites before.
The DD/MM/YYYY format would be best, they don't need to read the day of the week too, I know that's more work.
I don't have any working code because I'm not sure on the best approach. Any comments, pointers or code would be really appreciated.

Answer 1

This should more or less do it for you:
<?php
$now = time();
$month = date('m', $now);
$day = date('j', $now);
$year = date('y', $now);
echo '<select>';
echo '<option value="Not Selected" disabled selected>Please select a date.</option>';
for ($m = $month; $m <= 12; $m++)
{
echo '<optgroup label="' . date("F", strtotime("$year-$m-01")) . '">';
$startDay = $m == $month ? $day : 1;
for ($d = $startDay; $d <= cal_days_in_month(CAL_GREGORIAN, $m, $year); $d++)
{
echo '<option value="' . $d . '">' . $d . '/' . $m . '/' . $year . '</option>' . "\n";
}
}
echo '</select>';
?>