Last day of previous months calculating wrong

Question

I'm having issues calculating the last day of the previous 12 months.

Here's the code I'm using:

    for ($i = 0; $i <= 12; $i++) {
        $start[] = date("Y-m-01", strtotime( date( 'Y-m-01' )." -$i months"));
        $end[] = date( 'Y-m-t', strtotime($start[$i]. -1*$i .' month') );

        echo $start[$i] . " - " . $end[$i] . "<br/>";
    }

This produces:

2015-10-01 – 2015-10-31
2015-09-01 – 2015-08-31
2015-08-01 – 2015-06-30
2015-07-01 – 2015-04-30
2015-06-01 – 2015-02-28
2015-05-01 – 2014-12-31
2015-04-01 – 2014-10-31
2015-03-01 – 2014-08-31
2015-02-01 – 2014-06-30
2015-01-01 – 2014-04-30
2014-12-01 – 2014-02-28
2014-11-01 – 2013-12-31
2014-10-01 – 2013-10-31

Notice that the last day for September is not correct (it's showing August 31st as the last day). This happens for multiple months.

Any ideas?

Answer 1

What is the desired result? I assume you're just trying to display the first and last days of the month? Your code iterates over $i. So every time it iterates, it's removing 0 months, 1 month, 2, 3, 4, 5... etc.

Just remove that code completely. Y-m-t will do.

for ( $i = 0; $i <= 12; $i++ ) {
    $start[] = date('Y-m-01', strtotime( date( 'Y-m-01' )." -$i months"));
    $end[]   = date('Y-m-t',  strtotime( $start[$i] ) );

    echo $start[$i] . " - " . $end[$i] . "<br/>";
}

Results in

2015-10-01 - 2015-10-31
2015-09-01 - 2015-09-30
2015-08-01 - 2015-08-31
2015-07-01 - 2015-07-31
2015-06-01 - 2015-06-30
2015-05-01 - 2015-05-31
2015-04-01 - 2015-04-30
2015-03-01 - 2015-03-31
2015-02-01 - 2015-02-28
2015-01-01 - 2015-01-31
2014-12-01 - 2014-12-31
2014-11-01 - 2014-11-30
2014-10-01 - 2014-10-31

Answer 2

I assume it's because of your iteration while setting $end[]. This, however seems to work:

for ($i = 0; $i <= 12; $i++) {
    $start[] = date("Y-m-01", strtotime( date( 'Y-m-01' )." - $i months"));
    $end[] = date("Y-m-t",strtotime("last day of " . date("Y-m", strtotime($start[$i]))));

    echo $start[$i] . " - " . $end[$i] . "\n";
}

Or as @Christian Varga answered:

$end[]   = date('Y-m-t',  strtotime( $start[$i] ) );

Which returns:

2015-10-01 - 2015-10-31
2015-09-01 - 2015-09-30
2015-08-01 - 2015-08-31
2015-07-01 - 2015-07-31
2015-06-01 - 2015-06-30
2015-05-01 - 2015-05-31
2015-04-01 - 2015-04-30
2015-03-01 - 2015-03-31
2015-02-01 - 2015-02-28
2015-01-01 - 2015-01-31
2014-12-01 - 2014-12-31
2014-11-01 - 2014-11-30
2014-10-01 - 2014-10-31

Example/Demo