PHP Mktime shows 2 March's when I dump foreach month - php

Question

I've been using the following function fine until the other day when the clocks went forward:
function months($month_format="F") {
$array = array();
for ($i = 1; $i <=12; $i++) {
$array[$i]['string'] = date($month_format, mktime(0,0,0,$i));
$array[$i]['int'] = date('m', mktime(0,0,0,$i));
}
return $array;
}
It outputs an array with:
string[]
int[]
Since the other day (like 2 days ago, when the clocks went forward in the UK), the function seems to be showing me 2 march months and 0 Februarys....
Very very strange...
I'm using rethinkdb with their eachPosTime function... not sure if this is causing it.
I tried using a different function, but still using mktime:
function months(){
$start_month = 1;
$end_month = 12;
$start_year = date("Y");
$array = array();
for($m=$start_month; $m<=12; ++$m){
echo $m.'<br>';
$array[$m]['string'] = date('F', mktime(0,0,0,$m));
$array[$m]['int'] = date('m', mktime(0,0,0,$m));
if($start_month == 12 && $m==12 && $end_month < 12)
{
$m = 0;
$start_year = $start_year+1;
}
//echo date('F Y', mktime(0, 0, 0, $m, 1, $start_year)).'<br>';
if($m == $end_month) break;
}
return $array;
}
Still, I am having no luck.
Check the image here, which shows the output of the months() function:
Output of the months() function

Answer 1

This is not to do with the clocks changing, but the time of the month, and the entirely unhelpful signature of the mktime function.
When you leave out parameters from a "mktime" call, they are filled in with today's date. In your case, you specified month without day or year, so when you ask for mktime(0, 0, 0, 2); it will fill in today's day and year, and look for the 29th February 2021 - a day that doesn't exist. Since the time library "overflows" dates, this becomes the 1st March.
The solution is to pass an explicit day to "mktime", as in mktime(0,0,0,$m,1) or to use a less confusing function.