Returning the day on any particular date (21st Century)

<?php
/**
 * This will accept three parameters of type integer, representing
 * a numerically written date, for instance, dd/mm/yy, assuming 2000 onwards.
 * It will then construct and return a string based on the numeric
 * date sent, so for instance 29/10/02 will return
 * Tuesday 29th October 2002. It will also work with future dates, which is
 * useful unless we start commonly using something different from the
 * gregorian calendar.
 *
 * @author: Shaun_B
 * @date:   2012-10-10
 * @todo:   Accept four-digit length years (2003 rather than 03)
 *      and also implement the 20th century bit, so that dates
 *      between 1900 - 1999 are accepted too.
 *
 **/
class DateClass {
    // Sets default year to zero (ie, 2000 etc...)
    public static function dateConstruct( $dd = null, $mm = null, $yy = 0 ) {
    // Number of days in each month (excluding leap-years)
    // We have special conditions later for leap-years and February 29th:
    $noOfDays = array( 1=>31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );
    // This will test each variable sent to the function
    // to see if it's not null and each is numeric:
    if( !$dd || !$mm ) {
        echo 'invalid or null date type, please enter numeric date as <br />';
        echo 'DD/MM/YY, ie, 28/02/10.';
        return;
    }
    // We'll transfer the sent variables to local variables:
    $day = $dd;
    $month = $mm;
    $year = $yy;
    // We get onto the real testing now, to check that
    // each numeric number entered is within the legal
    // range (ie, DD/MM/YY):
    if( $month<1 || $month>12 ) {
        echo 'Month invalid, reset to default. <br />';
        $month = 01;
    }
    if( $day<1 || $day>31 ) {
        echo 'Day invalid, reset to default.<br />';
        $day = 01;
    }
    if( $year<0 || $year>99 ) {
        echo 'Year is invalid, reset to default.<br />';
        $year = 01;
    }
    // Now further validation on the day to check for
    // specific months and leap-years etc...
    if( $day>29 && $month==2 ) {
        echo 'Day invalid, reset to default.<br />';
        $day = 01;
    }
    // Now let's do some calculations for the leap-year
    // Remember that 2000 was a leap year and 1900 wasn't:
    if( $day==29 && $month==2 && ((2000-$year)%4!=0) ) {
        echo 'Not a leap year, reset to default.<br />';
        $day = 28;
    }
    // Next, to validate the rest of the months:
    if( $day>$noOfDays[ $month ] && $month!=2 ) {
        echo 'Day not valid, reset to default.<br />';
        $day = 01;
    }
    // Finally, let's print out the date as we need it:
    if( $year<10 ) {
            $returnValue = (string) DateClass::dayFromDate( $day, $month, $year )
            . 'day ' . $day . DateClass::suffix( $day ) . ' '
            . DateClass::monthAsString( $month ) . ' 200' . $year . '<br />';
        } else {
            $returnValue = (string) DateClass::dayFromDate( $day, $month, $year )
            . 'day ' . $day . DateClass::suffix( $day ) . ' '
            . DateClass::monthAsString( $month ) . ' 20' . $year . '<br />';
        }
        return $returnValue;
    }
    // Here are the functions to echo values as strings:
    public static function monthAsString( $month = null ) {
        // Here are the months of the year:
        $monthToString = array( 1=>'January', 'February', 'March',
                'April', 'May', 'June', 'July', 'August',
                'September', 'October', 'Novermber', 'December' );
        if( $month>0 && $month<13 ) {
            return $monthToString[ $month ];
        } else {
            return 'Month not set';
        }
    }
    // This will deal with the suffix of the numeric day,
    // ie, 01/xx/xx will be 1st/xx/xx:
    public static function suffix( $day = null ) {
        switch( (int) $day ) {
            case 1:
                return 'st';
                break;
            case 2:
                return 'nd';
                break;
            case 3:
                return 'rd';
                break;
            case 21:
                return 'st';
                break;
            case 22:
                return 'nd';
                break;
            case 23:
                return 'rd';
                break;
            case 31:
                return 'st';
                break;
            default:
                return 'th';
                break;
        }
    }
    public static function dayFromDate( $d = null, $m = null, $y = null ) {
        $day = $d;
        $month = $m;
        $year = $y;
        // This is for the day validation. If the day is in the
        // 20th century (1901 - 1999), here's the correct look-up
        // table for the days according to my maths (has eight
        // elements to stop errors):
        $daysOfWeek20th = array( 'Mon', 'Tues', 'Wednes',
            'Thurs', 'Fri', 'Satur', 'Sun', 'Mon' );
        // Here is the same look-up table for the 21st century:
        $daysOfWeek21st = array ( 'Sun', 'Mon', 'Tues',
            'Wednes', 'Thurs', 'Fri', 'Satur', 'Sun', 'Mon' );
        // Here is the month codes which will be used in the
        // algorithm later on:
        $monthCodes = array( 1=>6, 2, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4, 6 );
        $a = $year+( abs( $year/4 ) );
        $x = $monthCodes[ $month ];
        $y = $day;
        $z = $a + $x + $y;
        $a = abs( $z );
        $c = round( $a );
        $v = $c % 7;
        while( $v<=0 ) {
            $v += 7;
        }
        $leapYear = (2000-$year)%4;
        // A bug in the algorithmn means that the year immediately proceeding
        // a leap year is mis-calculated, so we need to increase $v by one:
        if($leapYear==3)
        {
            $v++;
        }
        // Another bug found: this one involves months after February on all
        // years but leap-years.
        if($month>=3 && $leapYear)
        {
            $v--;
        }
        if( $month>=1  && $month<=2 ) {
            return $daysOfWeek21st[ $v-1 ];
        } else if( $month>=3 ) {
            return $daysOfWeek21st[ $v ];
        } else {
            return 'Day unknown';
        }
    }
}
?>