Unable to understand behavior of the DateTime class in PHP

Question

I am using LAMP in Kubuntu 14.04 with PHP 5.6.23.

When using DateTime in follwing cases:

1.

print_r((new DateTime('2016-02-31'))->format('M/d/Y')); 
// Mar/02/2016 (no errors, why?)

2.

print_r((new DateTime('2016-02-32'))->format('M/d/Y')); 
// Error - DateTime::__construct(): Failed to parse time string-
// (2016-02-32) at position 9 (2): Unexpected character

Why the first case give me no error, as there is no 31st date of February month?

References supporting answer are requested

Answer 1

From the php docs:

It is possible to over- and underflow the dd and DD format. Day 0 means the last day of previous month, whereas overflows count into the next month. This makes "2008-08-00" equivalent to "2008-07-31" and "2008-06-31" equivalent to "2008-07-01" (June only has 30 days).

Note that as of PHP 5.1.0 the day range is restricted to 0-31 as indicated by the regular expression above. Thus "2008-06-32" is not a valid date string, for instance.

This makes it pretty clear.

In the user notes Mirek also suggest to use mktime if you need:

unlimited over/underflow for date calculations (for example 2015-01-40 to 2015-02-09)