Grab all Wednesdays in a given month in PHP

Question

This is the function I'm trying to write:

function getWednesdays($month, $year) {
   // Returns an array of DateTimes representing all Wednesdays this month.
}

Any ideas? Thanks-

Answer 1

With PHP5.3

function getWednesdays($y, $m)
{
    return new DatePeriod(
        new DateTime("first wednesday of $y-$m"),
        DateInterval::createFromDateString('next wednesday'),
        new DateTime("last day of $y-$m")
    );
}

Usage:

foreach (getWednesdays(2010, 11) as $wednesday) {
    echo $wednesday->format("l, Y-m-d\n");
}

Output:

Wednesday, 2010-11-03
Wednesday, 2010-11-10
Wednesday, 2010-11-17
Wednesday, 2010-11-24

Note that this will exclude the end date, so if the last day of $y-$m happens to be a Wednesday, it won't be in the list. You have to add a day to the end date, to include it. To include it, change the relative format in the end date to

new DateTime("next month $y-$m-01")

which will then set the end date to the first day of the next month,

---

With PHP < 5.3

function getWednesdays($y, $m)
{
    $ts  = strtotime("first wednesday $y-$m-01");
    $end = strtotime("last wednesday $y-$m");
    $wednesdays = array();
    while($ts <= $end) {
        $wednesdays[] = $ts;
        $ts = strtotime('next wednesday', $ts);
    }
    return $wednesdays;
}

Usage:

foreach (getWednesdays(2010, 11) as $wednesday) {
    echo date("l, Y-m-d\n", $wednesday);
}

Same output as above (Run on Codepad).

Note that this does not work for any version prior to 5.3 due to changes in the relative formats parser. If you want to use this with PHP 5.3+ you have to change first Wednesday $y-$m-01 to first Wednesday of $y-$m-01 (mind the "of"). Also, just like in the DateTime version, the end date will not be included.

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Further reading:

• DateTime in PHP Manual
• Relative DateTime Formats
• Derick Rethans: Advanced Date/Time Handling (ZendCon 10)
• Relative item in date strings (mirror)