php weeks between 2 dates

echo datediff('ww', '9 July 2003', '4 March 2004', false);

Find the function on the site below: http://www.addedbytes.com/code/php-datediff-function/

UPDATE

Link is now broken (Sept 2017), so function below pulled from webarchive:

<?php

/**
 * @param $interval
 * @param $datefrom
 * @param $dateto
 * @param bool $using_timestamps
 * @return false|float|int|string
 */
function datediff($interval, $datefrom, $dateto, $using_timestamps = false)
{
    /*
    $interval can be:
    yyyy - Number of full years
    q    - Number of full quarters
    m    - Number of full months
    y    - Difference between day numbers
           (eg 1st Jan 2004 is "1", the first day. 2nd Feb 2003 is "33". The datediff is "-32".)
    d    - Number of full days
    w    - Number of full weekdays
    ww   - Number of full weeks
    h    - Number of full hours
    n    - Number of full minutes
    s    - Number of full seconds (default)
    */

    if (!$using_timestamps) {
        $datefrom = strtotime($datefrom, 0);
        $dateto   = strtotime($dateto, 0);
    }

    $difference        = $dateto - $datefrom; // Difference in seconds
    $months_difference = 0;

    switch ($interval) {
        case 'yyyy': // Number of full years
            $years_difference = floor($difference / 31536000);
            if (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom), date("j", $datefrom), date("Y", $datefrom)+$years_difference) > $dateto) {
                $years_difference--;
            }

            if (mktime(date("H", $dateto), date("i", $dateto), date("s", $dateto), date("n", $dateto), date("j", $dateto), date("Y", $dateto)-($years_difference+1)) > $datefrom) {
                $years_difference++;
            }

            $datediff = $years_difference;
        break;

        case "q": // Number of full quarters
            $quarters_difference = floor($difference / 8035200);

            while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($quarters_difference*3), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
                $months_difference++;
            }

            $quarters_difference--;
            $datediff = $quarters_difference;
        break;

        case "m": // Number of full months
            $months_difference = floor($difference / 2678400);

            while (mktime(date("H", $datefrom), date("i", $datefrom), date("s", $datefrom), date("n", $datefrom)+($months_difference), date("j", $dateto), date("Y", $datefrom)) < $dateto) {
                $months_difference++;
            }

            $months_difference--;

            $datediff = $months_difference;
        break;

        case 'y': // Difference between day numbers
            $datediff = date("z", $dateto) - date("z", $datefrom);
        break;

        case "d": // Number of full days
            $datediff = floor($difference / 86400);
        break;

        case "w": // Number of full weekdays
            $days_difference  = floor($difference / 86400);
            $weeks_difference = floor($days_difference / 7); // Complete weeks
            $first_day        = date("w", $datefrom);
            $days_remainder   = floor($days_difference % 7);
            $odd_days         = $first_day + $days_remainder; // Do we have a Saturday or Sunday in the remainder?

            if ($odd_days > 7) { // Sunday
                $days_remainder--;
            }

            if ($odd_days > 6) { // Saturday
                $days_remainder--;
            }

            $datediff = ($weeks_difference * 5) + $days_remainder;
        break;

        case "ww": // Number of full weeks
            $datediff = floor($difference / 604800);
        break;

        case "h": // Number of full hours
            $datediff = floor($difference / 3600);
        break;

        case "n": // Number of full minutes
            $datediff = floor($difference / 60);
        break;

        default: // Number of full seconds (default)
            $datediff = $difference;
        break;
    }

    return $datediff;
}

Here's an alternative solution using DateTime:-

function datediffInWeeks($date1, $date2)
{
    if($date1 > $date2) return datediffInWeeks($date2, $date1);
    $first = DateTime::createFromFormat('m/d/Y', $date1);
    $second = DateTime::createFromFormat('m/d/Y', $date2);
    return floor($first->diff($second)->days/7);
}

var_dump(datediffInWeeks('1/2/2013', '6/4/2013'));// 21

See it working

$diff = strtotime($dateto, 0) - strtotime($datefrom, 0);
echo floor($diff / 604800);

This work great

function weeks_between($datefrom, $dateto)
    {
        $datefrom = DateTime::createFromFormat('d/m/Y H:i:s',$datefrom);
        $dateto = DateTime::createFromFormat('d/m/Y H:i:s',$dateto);
        $interval = $datefrom->diff($dateto);
        $week_total = $interval->format('%a')/7;
        return floor($week_total);

    }

weeks_between("25/02/2000 11:30:00","05/06/2015 11:29:59")