Calendar Class

<?php
	/**
	*Class which contains functions to build Calendar for a definite month
	*General algorithm is as following:
	*We Build the array of days of month and put 0 where there is no value and then 
	*display it in a way we want. We can simply display it, we can add news, appointments
	* and whatever you like to the every date of the month. The aim oth this class is to show
	* how to build the calendar itself, not how to display or work with it
	*/
	class Calendar
	{
		/**
		*Number of the month for which the calendar is built
		*/
		var $month;
		/**
		*Number of the year
		*/
		var $year;
		/**
		*Current day. It is used for building the calendar
		*/
		var $day = 0;
		/**
		*Maximum days in current month
		*/
		var $maxday;
		/**
		*Array of the month's days
		*/
		var $monthArray = array();
		
		/**
		*Constructor of the class. In it we get the shift towards 
		*current month from address line bye the $_GET method
		*Then we sum it with the current month. If the number is greater
		* than 12, we add one year and subtract 12 months from the month value
		*If the number less than zero, we behave quite opposite - add 12 months
		* and subtract one year.
		*If everything is OK, we simply put current year in the year property of 
		*the object
		*/
		function Calendar()
		{
			$this->month = date('n')+(integer)$_GET['smon'];
			if ( $this->month >12 )
			{
				$this->month = $this->month - 12;
				$this->year = date('Y');
			}
			else
			{
				if ( $this->month < 0 )
				{
					$this->month = 12 + $this->month;//as $this->month<0, we add it
					$this->year = date('Y') - 1;
				}
				else
				{
					$this->year = date('Y');
				}
			}
			$this->_getMaxDays();
		}
		
		/**
		*Function calculates number of the days in the month
		*@return integer $maxday Result is put to the property of the object
		*/
		function _getMaxDays()
		{
			$time=getdate(mktime(0,0,0,$this->month+1, 1, $this->year)-1);
			$this->maxday = $time['mday'];
		}
		
		/**
		*Function builds the week of a definite month
		*<p>
		*It takes all arguments from the object's properties
		*<p>
		*It behaves in the following way:
		*<p>
		* If the value of the current day is zero, then it is the first week of the
		* month and we move towards cycling the number of days of the week up to the 
		* number of the week for the first day of the month. When we reach it, we begin
		* to add day of the month to the week array and increment the number of the day
		*<p>
		* If the Day value is non-zero, then we increment the number of the day and then 
		* check, if it is less of equal to the maximal value of the day in this month.
		* If it is greater, we put zeroes to the week array, otherwise we put number of
		* the day
		*/
		function _buildWeek($begday)
		{
			if ( $this->day == 0 )
			{
				for ($i = 0; $i<7; $i++)
				{
					if ( $i >= $begday )
					{
						$this->day++;
						$week[$i] = $this->day;
					}
					else
					{
						$week[$i] = 0;
					}
				}
			}
			else
			{
				for ($i = 0; $i<7; $i++)
				{
					$this->day++;
					if ( $this->day <= $this->maxday )	
					{
						$week[$i] = $this->day;
					}
					else
					{
						$week[$i] = 0;
					}
				}
			}
			return $week;
		}
		
		/**
		*Function builds month itself
		*It cycles from 0 to 6 weeks (maximum) and builds the array of month's days
		*/
		function _BuildMonth()
		{
			/**
			*Here if we subtract 1, week will begin with Monday, if we will not, Sunday will
			*be the first day
			*/
			$startday = (integer)strftime('%w', mktime(0,0,0,$this->month, 1, $this->year)) - 1;
			for ( $i = 0; $i < 7; $i++ )
			{
				$this->monthArray[$i] = $this->_buildWeek($startday);
				if ( $this->monthArray[$i][6] == 0 )
				{
					break;
				}
			}
		}
		
		/**
		*Function displays the calendar to the user. 
		*It is only an example. Here we cycle through weeks, then view each day of the week
		*If there is not "0", then we display the number, otherwise, we echo &nbsp;
		*/
		function DisplayMonth()
		{
			$this->_BuildMonth();
			$weeks=sizeof($this->monthArray);
			echo "<table>n";
			for ( $i = 0; $i < $weeks; $i++ )
			{
				echo "<tr>n";
				for ( $j = 0; $j < 7; $j++)
				{
					echo "<td>n";
					if ($this->monthArray[$i][$j] != 0)
					{
						echo $this->monthArray[$i][$j]."n";
					}
					else
					{
						echo "&nbsp;n";
					}
					echo "</td>n";
				}
				echo "</tr>n";
			}
			echo "</table>n";
		}
	}
?>