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Two components included with Active Server Pages can be used to create page counters. Using page counters, you can track the number of times that a particular page has been requested. You can display this information on the page itself, or you can keep track of this information for your own purposes.

The Counters Component

The Counters component can be used to count the number of times a page has been requested, but it can also be used to count anything else as well. For example, you can use it to count the number of visitors to your Web site, the number of times an advertisement has been clicked, or even the number of times someone has requested a Web page with the Netscape 2.0 browser.

You can create only one instance of this component. However, once you create an instance of the component, you can create as many individual counters as you need. The single Counter component can contain many individual counters with different names.

Because you can create only one Counters component, it's a good idea to create the Component within the Global.asa file. This will guarantee that only one instance of the Counters component is created when your Web server starts.

Here's an example of how you can create the component within the Global.asa file:

The Microsoft extended HTML <OBJECT> tag is used here to create an instance of the Counters component named MyCount with application-wide scope. Remember to use the <OBJECT> tag outside any scripts within the Global.asa file. Once an instance of the Counters component has been created in this way, its methods can be accessed from any page within your specific application.

The Counters component has four methods. The following list details how each method is used:

Get (counter name). This method returns the current value of a counter. If the counter doesn't exist, it is created and set to 0.
Increment (counter name). This method adds 1 to the current value of a counter. If the counter doesn't exist, it is created and its value set to 1.
Remove (counter name). This method destroys a counter.
set (counter name, integer). This method accepts two arguments. The first argument is the name of a counter, and the second argument is an integer value. The method adds the integer to the counter. If the counter doesn't exist, the counter is created with the specified value.

Once an instance of the Counters component has been created in the Global.asa file, you can increment and decrement individual counters within any Active Server Page. A counter created in one page can be incremented, decremented, or removed in another page. Following is an example of how you can use the Counters component to keep track of the number of times a particular page has been requested:

<HTML>
<HEAD><TITLE>Some Page</TITLE></HEAD>
<BODY>
This page has been requested
<%=Mycount.Increment("PageCnt") %>
times.
</BODY>
</HTML>

The first time this page is requested, a counter named PageCnt is created and set to the value 1. Subsequent requests increment the value of this counter by 1. The PageCnt counter reflects the number of times the page has been requested.

What happens if your server is unexpectedly shut down? The counters you create with the Counters component are persistent. They're saved in a file named counters.txt. If the server shuts down, the counters still exist when it starts again.

Admittedly, the counter is a little boring. Most counters you see on Web sites use images for their counters. You can do this as well:

<%
SUB ShowImagoCnt(TheNum)
CntStr=CSTR(TheNum)
FOR i=1 TO LEN(CntStr)
CntPart=MID(CntStr,i,1)
%>
<IMG SRC="<%=CntPart%>.gif" ALT="<%=CntPart%>">
<%
NEXT
END SUB
%>
<HTML>
<HEAD><TITLE>Some Page</TITLE></HEAD>
<BODY>
This page has been requested-
<%
ShowImageCnt MyCount.Increment("PageCnt")
%>
times.
</BODY>
</HTML>

This new Active Server Page also displays a page counter. However, the page count is displayed by using images rather than text. The procedure named ShowImageCnt first converts the page count to a string. Next, a FOR...NEXT loop is used to walk through each numeral in the string and display a corresponding image.

To use this example, you'll need 10 images named 0.gif, 1.gif, 2.gif, and so on. You can create these images yourself However, a number of Internet sites have libraries of counter images that you can download freely (check the graphics section at your favorite Internet directory).

The Page Counter Component

There's a second component that you can use to display a page counter on a Web page. By using the Page Counter component, you can track the number of times a particular Web page has been opened.

The Page Counter component is much less flexible than the Counters component. It can't be used to track anything other than a page's hit count. This component has the following two methods:

Hits (path). This method returns the number of times a page with the specified path has been opened. If no path is provided, the method returns this value for the current page.
Reset (path). This method resets the count to 0 for the page with the specified path. If no path is provided, the value for the current page is reset.

Unlike when using the Counters component, you don't need to create an instance of the Page Counter component within the Global.asa file. You can create an instance of the component in the same page in which you use it, like this:

<HTML>
<HEAD><TITLE> Page Counter Example </TITLE></HEAD>
<BODY>
<%
Set MyHits=Server.CreateObject("MSWC.PageCounter")
%>
This page has been viewed
<%=MyHits.Hits%>
times.
</BODY>
</HTML>

This Active Server Page simply displays the number of times the current page has been opened. The Hits method is called without any parameters, which results in the hit count for the current page being returned.

Summary

This chapter showed you how to incorporate advertisements into your Web pages. You learned how to use the Ad Rotator component to display a series of banner advertisements. You also learned how to use the Content Rotator component to randomly display different HTML content strings. Finally, you learned how to use two components that can be used to display a page counter on a Web page.