Calculating and adjusting dates based on exceptions (PHP) - php

Question

Here are the rules:
The adding of days is always by 15s (ex. 15, 30, 45, 60, etc.)
When the maturity date day falls on the 15th or end of the month
(ex. 30 or 31 depends on the month, 28 or 29 every February depends
if leap year) when adding days (as mention above) the date
should fall ONLY to 15th or end of month.
When the maturity date day does not fall every 15th or end of the
month just normally add days.
When the date is February 14 and add 15 days it should return 02/29 if leap year or 02/28 if not leap year.
Here is my code but, I am getting 1 error and inconsistency.
Catchable fatal error when the date is 02/29/2020 and add 30 days.
What can I do to accommodate this rules?
function adjustDate($maturitydate, $add) {
$nodays = '+'.$add.' days';
$date = new DateTime($maturitydate);
$matdt = $date->modify($nodays);
$ismaturitydateendofmonth = check_end_of_month($maturitydate);
if($date->format('d') == 15) {
$matdt = $matdt->format('m/15/Y');
}
else if($ismaturitydateendofmonth == '1'){
$matdt->modify('last day of this month');
}
else{
$matdt = $matdt->format('m/d/Y');
}
return $matdt;
}
function check_end_of_month($date){
//adds 1 day to date
$Temp = date('m/d/Y',strtotime("+1 day", strtotime($date)));
//get the month of each date
$tempmonth = date('m', strtotime($Temp));
$datemonth = date('m', strtotime($date));
//check if the months are equal
if($tempmonth != $datemonth){
return '1';
}
else{
return '0';
}
}

Answer 1

The code below will fix all the exceptions and inconsistencies.
$matdt = $maturitydatefrom;
for ($x = 0; $x < $chknumdif; $x++) {
$matdt = getNextDuedate($matdt, $maturitydatefrom);
}
function getNextDuedate($prevdate, $maturitydate){
$maturityday = date('d', strtotime($maturitydate));
$prevday = date('d', strtotime($prevdate));
$prevmonth = date('m', strtotime($prevdate));
$prevyear = date('Y', strtotime($prevdate));
$prevlastday = date('t', strtotime($prevdate));
$maturitylastday = date('t', strtotime($maturitydate));
$isendofmonth = check_end_of_month($maturitydate);
if($maturityday == $maturitylastday || $maturityday == 15){
if($prevday == 15){
$duedate = $prevmonth . '/' . $prevlastday . '/' . $prevyear;
}
else{
$prevdate = date('m/d/Y', strtotime("+1 month", strtotime($prevdate)));
$duedate = date('m', strtotime($prevdate)) . '/15/' . date('Y', strtotime($prevdate));
}
}
else{
if($prevday < 15){
if($prevmonth == '2' && $prevday == '14'){
$duedate = $prevmonth . '/' . $prevlastday . '/' . $prevyear;
}
else{
$duedate = $prevmonth . '/' . ($prevday + 15) . '/' . $prevyear;
}
}
else if($prevday > 15){
if($maturityday < 15){
$prevdate = date('m/d/Y', strtotime("+1 month", strtotime($prevdate)));
$duedate = date('m', strtotime($prevdate)) . '/' . $maturityday . '/' . date('Y', strtotime($prevdate));
}
else{
$prevdate = date('m/d/Y', strtotime("+1 month", strtotime($prevdate)));
$duedate = date('m', strtotime($prevdate)) . '/' . ($maturityday - 15) . '/' . date('Y', strtotime($prevdate));
}
}
}
return $duedate;
}