Case Study: An Affiliate System With ASP

Case Study: An Affiliate System With ASP - The ShowLogin function
(Page 4 of 7 )

ShowLogin is used in combination with ProcessLogin to get the affiliates email address and password and to verify them against the database respectively. First off, the ShowLogin function displays a simple HTML form. When the login button is clicked, a small bit of JavaScript is used to make sure that both of their fields were completed:

<script language="Javascript">

function CheckForm(varForm)
{

if (document.frmLogin.txtEmail.value == "")
{
alert('Please enter your email address (eg johndoe@hotmail.com)');
document.frmLogin.txtEmail.focus();
return false;
}
if (document.frmLogin.txtPassword.value == "")
{
alert("Please enter your password");
document.frmLogin.txtPassword.focus();
return false;
}
return true;
}
</script>

The login's <form> tag contains the onSubmit event, meaning that when the form is submitted, the JavaScript function CheckForm will be called. It also contains a where query string variable that's set to processlogin:

<form onSubmit="return CheckForm('this')" name="frmLogin" action="affiliates.asp?where=processlogin" method="post">

When the form is submitted, affiliates.asp calls the ProcessLogin function, which simply takes the affiliates email and password and checks them with a SELECT query, similar to the one shown below:

strQuery = "SELECT COUNT(*) FROM Affiliates WHERE email='" & txtEmail & "' AND password='" & txtPassword & "'"

if objRS.State = 1 then objRS.Close
objRS.Open strQuery

intCount = CInt(objRS.Fields(0).value)
if intCount > 0 then

'The user exists, we will set their login details
'to a session variable

Session.Contents("affEmail") = Request("txtEmail")

if intRemember = "1" then

'Set the cookies so the user is remembered by the login form
Response.Cookies("aEmail") = Request("txtEmail")
Response.Cookies("aPass") = Request("txtPassword")

end if

Response.Redirect "affiliates.asp?where=link"

else

'The user doesn't exist in the affiliates table
%>
<span class="blueHeader">Affiliate Not Found</span>
<br><br>
<span class="bodyText">
No affiliate account with the email address "<%=txtEmail%>" was found.
Please click on the button below to go back and try again.
<br><br>
<a href="javascript:history.go(-1)"><img border="0" src="rel.gif"></a>
</span>
<%
end if

As the code shows, a session variable called affEmail is set. Two cookie variables are also set. These are used to pre-fill the login form if the user ticked the "remember me" checkbox.

At this point the affiliate is logged in and will want to do one of three things: build links, check his click-thru rate, or check his affiliate sales. We will take a look at these functions on the next page.
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