Sams Teach Yourself PHP, MySQL and Apache All in One (2012)

We pick up the entirely new code at line 66 of Listing 24.3. Because the table will be indexed by days of the week, we loop through an array of day names in lines 70–72, printing each in its own table cell, on line 71. All the real magic of the script happens in the final for statement beginning on line 73.

In line 73, we initialize a variable called $count and ensure that the loop will end after 42 iterations. This is to make sure that we will have enough cells to populate with date information, taking into consideration that a four-week month might actually have partial weeks at the beginning and the end, thus the need for six 7-day weeks (rows).

Within this for loop, we transform the $start variable into a date array with getdate(), assigning the result to $dayArray (line 73). Although $start is the first day of the month during the loop’s initial execution, we will increment this timestamp by the value of ADAY (24 hours) for every iteration (see line 85).

On line 75, we test the $count variable against the number 7, using the modulus operator. The block of code belonging to this if statement will therefore be run only when $count is either zero or a multiple of 7. This is our way of knowing whether we should end the loop altogether or start a new row, where rows represent weeks.

After we have established that we are in the first iteration or at the end of a row, we can go on to perform another test on line 76. If the mon (month number) element of the $dayArray is no longer equivalent to the $month variable, we are finished. Remember that $dayArray contains information about the $start timestamp, which is the current place in the month that we are displaying. When $start goes beyond the current month, $dayArray["mon"] will hold a different figure than the $month number provided by user input. Our modulus test demonstrated that we are at the end of a row, and the fact that we are in a new month means that we can leave the loop altogether. Assuming, however, that we are still in the month that we are displaying, we end the row and start a new one on line 79.

In the next if statement, on line 82, we determine whether to write date information to a cell. Not every month begins on a Sunday, so it’s likely that our rows will contain an empty cell or two. Similarly, few months will finish at the end of one of our rows, so it’s also likely that we will have a few empty cells before we close the table.

We have stored information about the first day of the $firstDayArray; in particular, we can access the number of the day of the week in $firstDayArray['wday']. If the value of $count is smaller than this number, we know that we haven’t yet reached the correct cell for writing. By the same token, if the value of the $month variable is no longer equal to $dayArray['mon'], we know that we have reached the end of the month (but not the end of the row, as we determined in our earlier modulus test). In either case, we write an empty cell to the browser on line 83.

In the final else clause on line 84, we can do the fun stuff. We have already determined that we are within the month that we want to list, and that the current day column matches the day number stored in $firstDayArray['wday']. Now we must use the $dayArray associative array that we established early in the loop to write the day of the month and some blank space into a cell.

Finally, on line 86, we need to increment the $start variable, which contains our date stamp. We just add the number of seconds in a day to it (we defined this value in line 2), and we’re ready to begin the loop again with a new value in $start to be tested. If you save this listing asshowcalendar.php, place it in your web server document root, and access it with your web browser, you should see something like Figure 24.2 (your month and year might differ).

Figure 24.2 The calendar form and script.

Adding Events to the Calendar

Displaying the calendar is great, but with just a few extra lines of code, you can make it interactive—that is, you can add and view events on a given day. To begin, let’s create a simple database table that holds event information. For purposes of simplicity, these events will occur on only a single day and only their start date and time will be shown. Although you can make the event entries as complex as you want, this example is here just to show the basic process involved.

The calendar_events table will include fields for the start date and time, the event title, and an event short description:

CREATE TABLE calendar_events (
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
event_title VARCHAR (25),
event_shortdesc VARCHAR (255),
event_start DATETIME
);

We can use the code in Listing 24.3 as our base (the script called showcalendar.php). In this new script, we add a link to a pop-up window as part of the calendar display. Each date is a link; the pop-up window calls another script that displays the full text of an event as well as provide the capability to add an event. To begin, add the following JavaScript code in the <head> area, before the opening <body> tag—after line 36 of the original script in Listing 24.3:

<script type="text/javascript">
function eventWindow(url) {
event_popupWin = window.open(url, 'event', 'resizable=yes, scrollbars=yes,
toolbar=no,width=400,height=400');
event_popupWin.opener = self;
}
</script>

This JavaScript function defines a 400×400 window that will call a URL we provide. We use this JavaScript function to replace what was line 85 of the original script in Listing 24.3; we now wrap the date display in this link to the JavaScript-based pop-up window, which calls a script namedevent.php. The new code is as follows:

echo "<td><a href=\"javascript:eventWindow('event.php?m=".$month.
"&d=".$dayArray['mday']."&y=$year');\">".$dayArray['mday']."</a>
<br/><br/>".$event_title."</td>\n";

Not only do we call the event.php file, but we also have to send along with it the date information for the particular link that is clicked. This is done via the query string, and you can see we’re sending along three variables—what will become $_GET['m'] for the month, $_GET['d'] for the day, and $_GET['y'] for the year.

Only one change remains for this particular script before we tackle the event.php script—adding an indicator to this particular view, if events do indeed exist. The query that checks for existing events on a given day appears at the onset of the else statement that was originally found at line 84. An entirely new else statement is shown; you can see that the database connection is made, a query is issued, and, if results are found, text is printed within the table cell for that day:

} else {
$mysqli = mysqli_connect("localhost", "joeuser", "somepass", "testDB");
$chkEvent_sql = "SELECT event_title FROM calendar_events WHERE
month(event_start) = '".$month."' AND
dayofmonth(event_start) = '".$dayArray['mday']."'
AND year(event_start) = '".$year."' ORDER BY event_start";
$chkEvent_res = mysqli_query($mysqli, $chkEvent_sql)
or die(mysqli_error($mysqli));

if (mysqli_num_rows($chkEvent_res) > 0) {
while ($ev = mysqli_fetch_array($chkEvent_res)) {
$event_title = stripslashes($ev['event_title']);
}
} else {
$event_title = "";
}
echo "<td><a href=\"javascript:eventWindow('event.php?m=".$month.
"&d=".$dayArray['mday']."&y=$year');\">".
$dayArray['mday']."</a><br/><br/>".$event_title."</td>\n";

unset($event_title);

$start += ADAY;
}

In Listing 24.4, you can see the entirely new script, which we’ll call showcalendar_withevent.php.

Listing 24.4 Calendar Display Script with Entry-Related Modifications