计算两个日期之间的日历月数[重复]

I would like to calculate number of calendar months between two days. For example:

2017-11-01 => 2017-11-30 = 1 (the same month)
2017-11-01 => 2017-12-01 = 2 (two different calendar months in the date)
2017-11-30 => 2017-12-01 = 2 (the same as above)
2017-11-15 => 2018-06-01 = 8 (6 + 2 different calendar months in the date)

How can I do that? So far I have:

$monthStart = new DateTime('2017-11-01');
$monthEnd = new DateTime('2017-12-01');
$dateDiff = $monthStart->diff($monthEnd);
$maxMonths = ($dateDiff->m + ($dateDiff->y*12) + $dateDiff->d>0?1:0);

But it doesn't work for some dates.

This QUESTION IS DIFFERENT from: Calculate the number of months between two dates in PHP? as I want to calculate the month every time the number for month changes. Not only when there is a 30 days difference between two days. Check the examples I have provided.

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$a = "2007-01-01";
$b = "2008-05-31";

$i = date("Ym", strtotime($a));
while($i <= date("Ym", strtotime($b))){
    echo $i."<br>";
    if(substr($i, 4, 2) == "12")
        $i = (date("Y", strtotime($i."01")) + 1)."01";
    else
        $i++;
}

output:

200701 200702 200703 200704 200705 200706 200707 200708 200709 200710 200711 200712 200801 200802 200803 200804 200805