Here's a very simple, but very complete, PHP script to print out a calendar. It does one thing, but does it well (which is how it should be). Neat bonus features include the ability to link certain days in the calendar to a web page - useful for a weblog.

Getting Calendar Variables

<?php

//This gets today's date
$date =time () ;

//This puts the day, month, and year in seperate variables
$day = date('d', $date) ;
$month = date('m', $date) ;
$year = date('Y', $date) ;

//Here we generate the first day of the month
$first_day = mktime(0,0,0,$month, 1, $year) ;

//This gets us the month name
$title = date('F', $first_day) ;

In the first part of our code we are setting some variables we will need later in the script. First we find out what today's date is using the time() function. We then use the date() function to format our date appropriately for the $day, $month, and $year variables. Finally we use it to generate the name of the month, which will be the title of our calendar.

Days of the Week

//Here we find out what day of the week the first day of the month falls on
$day_of_week = date('D', $first_day) ;

//Once we know what day of the week it falls on, we know how many blank days occure before it. If the first day of the week is a Sunday then it would be zero
switch($day_of_week){
case "Sun": $blank = 0; break;
case "Mon": $blank = 1; break;
case "Tue": $blank = 2; break;
case "Wed": $blank = 3; break;
case "Thu": $blank = 4; break;
case "Fri": $blank = 5; break;
case "Sat": $blank = 6; break;
}

//We then determine how many days are in the current month
$days_in_month = cal_days_in_month(0, $month, $year) ;

Next we count the total days of the month. Now that we know how many 'blank' days we need, and how many total days are in the month we can start to generate our calendar.

Headings and Blank Calendar Days

//Here we start building the table heads
echo "<table border=1 width=294>";
echo "<tr><th colspan=7> $title $year </th></tr>";
echo "<tr><td width=42>S</td><td width=42>M</td><td width=42>T</td><td width=42>W</td><td width=42>T</td><td width=42>F</td><td width=42>S</td></tr>";

//This counts the days in the week, up to 7
$day_count = 1;

echo "<tr>";
//first we take care of those blank days
while ( $blank > 0 )
{
echo "<td></td>";
$blank = $blank-1;
$day_count++;
}

The first part of this code very simply echos the table tags, the month name, and the headings for the days of the week. Then we start a while loop. What we are doing is echoing empty table details, one for each blank day we count down. Once the blank days are done it stops. At the same time, our $day_count is going up by 1 each time through the loop. This is to keep count so that we do not try to put more than seven days in a week.

Days of the Month

//sets the first day of the month to 1
$day_num = 1;

//count up the days, untill we've done all of them in the month
while ( $day_num <= $days_in_month )
{
echo "<td> $day_num </td>";
$day_num++;
$day_count++;

//Make sure we start a new row every week
if ($day_count > 7)
{
echo "</tr><tr>";
$day_count = 1;
}
}

Our loop also contains a conditional statement. This checks if the days of the week have reached 7, the end of the week. If it has, it starts a new row, and resets the counter back to 1 (the first day of the week).

Finishing the Calendar

//Finaly we finish out the table with some blank details if needed
while ( $day_count >1 && $day_count <=7 )
{
echo "<td> </td>";
$day_count++;
}

echo "</tr></table>";