How do I find what day the last saturday of the current month is in PHP?

This works for most months, but for example, April 2011 has 5 saturdays, so this returns 23 instead of 30.

$last_saturday = date("j", strtotime('Fourth Saturday'.date('F o')));

last saturday seems to be interpreted as "previous saturday" in some constellations.

This is what works for me on PHP 5.3 on Windows 7: Jump to next month's first day, and look for last saturday.

 $nextMonthStart = mktime(0,0,0,date('m')+1,1,date('Y'));
 $last_saturday = date("d.m.Y",strtotime("previous saturday", $nextMonthStart));

works for me even in the edge case that the first day of next month is a saturday.

Interestingly enough, strtotime("last saturday of this month") does exactly that.

See Supported Date and Time Formats for more, particularly the section on Relative Formats.

These days people use strtotime too liberally... if you want to be real hardcore (and reinvent the wheel a bit) you can use this piece of code I wrote for Moodle back in the day, which I guess has some novelty value. I copied it from here.

The last Sunday of April 2011 is find_day_in_month(-1, 0, 4, 2011), which means "start searching from the last day of April 2011 backwards and tell me when the first Sunday you find is".

See it in action.

/**
 * Calculate the number of days in a given month
 *
 * @param int $month The month whose day count is sought
 * @param int $year The year of the month whose day count is sought
 * @return int
 */
function days_in_month($month, $year) {
   return intval(date('t', mktime(12, 0, 0, $month, 1, $year)));
}


/**
 * ?
 *
 * @todo Document what this function does
 * @param int $startday Defines the day from which to start searching (absolute value) and the direction in which to search (sign)
 * @param int $weekday -1 if you don't want the function to match a specific weekday; 0 to 6 to match specific weekdays
 * @param int $month The month wherein the day is sought
 * @param int $year The year wherein the day is sought
 * @return int
 */
function find_day_in_month($startday, $weekday, $month, $year) {
    $daysinmonth = days_in_month($month, $year);

    if($weekday == -1) {
        // Don't care about weekday, so return:
        //    abs($startday) if $startday != -1
        //    $daysinmonth otherwise
        return ($startday == -1) ? $daysinmonth : abs($startday);
    }

    // From now on we 're looking for a specific weekday

    // Give "end of month" its actual value, since we know it
    if($startday == -1) {
        $startday = -1 * $daysinmonth;
    }

    // Starting from day $startday, the sign is the direction

    if($startday < 1) {

        $startday = abs($startday);
        $lastmonthweekday  = strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year));

        // This is the last such weekday of the month
        $lastinmonth = $daysinmonth + $weekday - $lastmonthweekday;
        if($lastinmonth > $daysinmonth) {
            $lastinmonth -= 7;
        }

        // Find the first such weekday <= $startday
        while($lastinmonth > $startday) {
            $lastinmonth -= 7;
        }

        return $lastinmonth;

    }
    else {

        $indexweekday = strftime('%w', mktime(12, 0, 0, $month, $startday, $year));

        $diff = $weekday - $indexweekday;
        if($diff < 0) {
            $diff += 7;
        }

        // This is the first such weekday of the month equal to or after $startday
        $firstfromindex = $startday + $diff;

        return $firstfromindex;

    }
}

https://github.com/briannesbitt/carbon

<?php
require 'vendor/autoload.php';

use Carbon\Carbon;

$date = Carbon::now();
$date = $date->lastOfMonth(Carbon::SATURDAY);
echo 'last saturday = '.$date->day;

$lastSaturDay= date('Y-m-d', strtotime('last saturday of this month'));

来源：https://stackoverflow.com/questions/5767561/how-do-i-find-what-day-the-last-saturday-of-the-current-month-is-in-php

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