Question

I know about the unwanted behaviour of PHP’s function

strtotime

For example, when adding a month (+1 month) to dates like: 31.01.2011 -> 03.03.2011

I know it’s not officially a PHP bug, and that this solution has some arguments behind it, but at least for me, this behavior has caused a lot waste of time (in the past and present) and I personally hate it.

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What I found even stranger is that for example in:

MySQL: DATE_ADD(‘2011-01-31’, INTERVAL 1 MONTH) returns 2011-02-28
or

C# where new DateTime(2011, 01, 31).AddMonths(1); will return 28.02.2011

wolframalpha.com giving 31.01.2013 + 1 month as input; will return Thursday, February 28, 2013

It sees to me that others have found a more decent solution to the stupid question that I saw alot in PHP bug reports “what day will it be, if I say we meet in a month from now” or something like that. The answer is: if 31 does not exists in next month, get me the last day of that month, but please stick to next month.

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So MY QUESTION IS: is there a PHP function (written by somebody) that resolves this not officially recognized bug? As I don’t think I am the only one who wants another behavior when adding / subtracting months.

I am particulary interested in solutions what also work not just for the end of the month, but a complete replacement of strtotime. Also the case strotime +n months should be also dealt with.

Happy coding!

Answer 1

Here’s the algorithm you can use. It should be simple enough to implement yourself.

• Have the original date and the +1 month date in variables
• Extract the month part of both variables
• If the difference is greater than 1 month (or if the original is December and the other is not January) change the latter variable to the last day of the next month. You can use for example t in date() to get the last day: date( 't.m.Y' )