<?php
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

    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;
}
//echo datediff('d','9/7/2006','12/7/2006')
//this will return the interval of day between the 2 days
?>