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PHP Function – Calculating Days In A Month

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All developers keep a tool box of useful functions and classes that they pick up or write along the way and this PHP came to me while I was writing an event calendar page for a customer.

I should mention that PHP does offer a cal_days_in_month function for PHP builds of PHP 4.0.7 and higher, but I prefer using the below function because it is guaranteed to work on all PHP version because it is based solely on logic.

The Code

function get_days_in_month($month, $year)
{
   return $month == 2 ? ($year % 4 ? 28 : ($year % 100 ? 29 : ($year %400 ? 28 : 29))) : (($month - 1) % 7 % 2 ? 30 : 31);
}

One line of logic provides the number of days in a month, taking into account leap years, and all on one line.

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Discussion

  1. noseyparker

    Thanks for your very helpful site! Love the tips.

  2. Michael Quinn

    Hi David,

    PHP versions 4&5 also offer the date("t") function which returns number of days in given month.

  3. paskuale

    michael is right: $totDays = date("t",strtotime($year.'-'.$_month.'-01'));

  4. Carl

    LOL.. Thanks Michael and Paskuale but I think you’re both missing the point! It’s nice to be told that we can get the days directly but the point about this function is that it’s an easily recognisable way to learn how ternary functions in PHP.

    Very useful for noobies such as myself – thanks David :)

  5. LOL.. Thanks Michael and Paskuale but I think you’

    LOL.. Thanks Michael and Paskuale but I think you’re both missing the point! It’s nice to be told that we can get the days directly but the point about this function is that it’s an easily recognisable way to learn how ternary functions in PHP.

    Very useful for noobies such as myself – thanks David :)

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