Examples


On the CD The quiz and origami store examples contain practical uses of cookies and session variables and are described in the next chapters. In Chapter 16, “Scaling Up Your Application,” you will read about using session variables to implement a password system. In this chapter, the examples are short and designed to encourage you to implement them and try them in various combinations. The scripts explained here show the use of cookies and sessions. The CD-ROM contains the code for the projects in the folder named chapter13code.

The setting of cookies is independent of ASP versus PHP, but not independent of a browser. The examples described here all make use of a form in which the user enters a name and a type of [dessert] cookie. Examples of cookies are things you eat, such as chocolate chips or lemon squares. Two computer cookies are set when the form is submitted: one named ‘cname’ for the username, and the other named ‘type’. The scripts cookies.asp and cookies.php each set the two cookies to persist only as long as the browser is open. The scripts cookies5min.asp and cookies5min.php each set the cookies to last for five minutes. The time interval of five minutes was chosen to give you enough time to exit the browser or go to another Web site, but not too long to try your patience. The intent is for you to perform two tests for each of the four scripts:

  • Execute the script, exit the browser, and then invoke the same browser again within five minutes.

  • Execute the script, do something else for more than five minutes, and return to the page of the script. You might need to force the browser to reload the page, which sometimes is a problem.

In the first case, the values of the cookies the name and the type of cookie, will not appear if the script last used was cookies.asp or cookies.php. The two values will appear if the script was cookies5min.asp or cookies5min.php. In contrast, if you invoke one of the five-minute scripts first and then cookies.asp or cookies.php, you will see the last set of values. The form is shown in Figure 13.6.

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Figure 13.6: Form to enter information to be stored as cookie. Web browser 2003 Netscape

Filling in the cookie, you will see something like what is in Figure 13.7.

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Figure 13.7: Form filled in.

Clicking on the send info button will produce the response Web page in Figure 13.8.

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Figure 13.8: Response to form.

Now we will examine the scripts for these pages. The first pair of scripts (one for ASP and one for PHP) produce cookies that last only as long as the browser is open. These are called cookies without expiration. This terminology does not mean that they never expire; it means, again, that they last as long and only as long as the browser is open. The second set of scripts sets an expiration time for the cookies. The expiration time chosen is quite short: five minutes. However, it is not associated with the running of the browser.

Cookies Without Expiration

The cookies.asp script, shown in Table 13.1, both handles the form data and displays the form for the user to enter data.

Table 13.1: ASP/JavaScript for Displaying Form and Handling Form

<%@ Language=JavaScript %>

Sets JavaScript as language

<%

Starts ASP

var submitted=String(Request.Form("submitted"));

Extracts submitted form data

if (submitted !="undefined") {

Checks if form has been filled out

sname=String(Request("cname"));

Set variable with form data

stype=String(Request("type"));

Set variable with form data

Response.Cookies("ccname") = sname;

Define cookie named “ccname” (or, to use the collection terminology, with the key “ccname”) to be the value of sname

Response.Cookies("ctype") = stype;

Define cookie named “ctype” (key “ctype”) to be the value of stype

%>

Close ASP

<html><head><title>Use cookie </title></head>

Normal HTML start

<body>

HTML body tag

<h1> Welcome

HTML

<%

Start ASP

Response.Write (sname + "</h1>\n");

Write out information given by form

Response.Write ("<br>You like "+ stype +" cookies.");

Write out information given by form

%>

Close ASP

<body>

HTML

</html>

HTML

<% }

Restart ASP to close off true if clause

else { %>

Start else clause and close ASP

<html><head><title>Form for cookies</title></head><body>

Normal HTML

<form action="cookies.asp" method=post>

Start form. Action handler is this script

Your name <input type=text name='cname' value='<%fromcookiename= Request.Cookies("ccname");

Input tag. This code will display the customer name data if it has been stored as a cookie. A local variable is used to hold the value

Response.Write(fromcookiename);%>'>

The variable is sent to the browser. If there was no cookie sent, nothing will be displayed

<br>

Line break

Your favorite cookie <input type=text name='type'

Input tag

value='<%fromcookietype=Request.Cookies("ctype");Response.Write(fromcookietype); %>'>

A local variable is set with the value from the cookie and written out

<br>

Line break

<input type=hidden name='submitted' value=TRUE>

Input tag for hidden value to indicate the form has been submitted

<input type=submit value='send info'><input type=reset value='reset'>

Input tag for the submit button

</form>

Form closing tag

</body>

Body closing tag

</html>

HTML closing tag

<% } %>

Restart ASP to close Else clause

The cookies.php, shown in Table 13.2, follows the same overall structure as the ASP file for the form handler and form. For the PHP case, you need to use the @ operator to suppress an error message in the case when no variable, including no cookie, exists.

Table 13.2: PHP Script for Displaying Form and Handling Form

<?php

Start PHP

if (@($submitted)) {

Check for is this form handler or form display

setcookie("ccname",$cname);

Set a cookie named “ccname” to be the value of $cname, which is one of the form inputs

setcookie("ctype",$type);

Set a cookie named “ctype” to be the value of $type, which is one of the form inputs

?>

Close PHP

<html><head><title>Use cookie </title></head>

Normal HTML

<body>

HTML

<h1> Welcome

HTML

<?

Restart PHP

print ("$cname! </h1>\n");

Display response

print ("<br>You like $type cookies.");

Display response

?>

Close PHP

</body>

Body close tag

</html>

HTML close tag

<? }

Restart PHP. Closing bracket for the if true clause on if submitted

else { ?>

Else clause. End PHP

<html><head><title>Form for cookies </title></head><body>

HTML

<form action="cookies.php" method=post>

Form tag

Your name <input type=text name='cname'

Input tag

value='<?print (@$ccname); ?>'>

Use $ccname for value of value attribute. Will use cookie if it exists. The @ prevents an error warning message

<br>

Line break

Your favorite cookie <input type=text name='type'

Input tag

value='<? print (@$ctype); ?>'>

Use $ctype for value of value attribute. Will use cookie if it exists. The @ prevents an error warning message

<br>

Line break

<input type=hidden name='submitted' value=TRUE>

Input tag for hidden submitted variable

<input type=submit value='send info'><input type=reset value='reset'>

Button labeled send info

</form>

Close form

</body>

Close body

</html>

Close HTML

<? }

End PHP. Closing bracket for the else clause

?>

Close PHP

Cookies with Expiration

To set a cookie with an explicit expiration time, ASP uses a property of the values in the Cookies collection; namely, the expires property. The first step is to determine the time. This is done using the JavaScript function for Date, which returns date and time. The next step for this example is to modify this value by FIVE minutes. This is done using methods of JavaScript date objects: getMinutes and setMinutes. The setMinutes method will do the right thing if the new value of minutes also changes the hours and day. Lastly, the calculated expiration must be converted to be the datatype expected by ASP. The expires property must be set with a time value in what ASP calls the Variant datatype. Most of the time, datatypes seem to take care of themselves, but this is one of the times when coding is necessary to change the datatype explicitly. The conversion (also called cast) from the JavaScript date datatype to Variant is done by the getVarDate method.

Here is the code for setting the cookies with an expiration time of five minutes from now:

    var later=new Date();     later.setMinutes(later.getMinutes()+5 );     Response.Cookies("ccname") = sname;     Response.Cookies("ccname").expires        = later.getVarDate();     Response.Cookies("ctype") = stype;     Response.Cookies("ctype").expires = later.getVarDate();

The PHP command to set a cookie to have an explicit expiration is the same command but with an additional parameter. The time() function returns a value of the current time. You need to add what you want to this value. For this example, it is written 5 times 60 just to make the five minutes clear. The PHP system does the correct thing with addition. The call to setcookie is:

    setcookie("ccname",$cname,time()+5*60);     setcookie("ctype",$type, time()+5*60);

Common Error

The setting of a cookie is done in the HTTP header. This means it must be done before anything is sent to the client. The following script would cause an error because the html tags at the start cause a header to be generated:

    <html><head><title>Form for cookies      </title></head> <body>     <?php     if (@($submitted)) {       setcookie("ccname",$cname);       setcookie("ctype",$type);       ?>       <html><head><title>Use cookie </title></head>       <body>       <h1> Welcome       <?       print ("$cname! </h1>\n");       print ("<br>You like $type cookies.");         ?>       </body>       </html>       <?     }     else { ?>       <form action="cookies.php" method=post>       Your name <input type=text name='cname'        value='<?print (@$ccname); ?>'>               <br>       Your favorite cookie <input type=text name='type'       value='<? print (@$ctype); ?>'>       <br>       <input type=hidden name='submitted' value=TRUE>       <input type=submit value='send info'>       <input type=reset value='reset'>       </form>       </body>       </html>       <? }     ?>

The PHP system would display the screen shown in Figure 13.9.

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Figure 13.9: Screen shot showing warning messages.

Examine Cookies

Once you have these scripts working, you should repeat the steps outlined previously to examine the cookies. The screen shot in Figure 13.5 shows the cookie ctype stored by Netscape 7.

Netscape 6.2 stores its cookies in a file called cookies.txt. There would be entries such as:

    sharon.ns.purchase.edu   FALSE   /   FALSE   1036259442      ctype 
chocolate+chip sharon.ns.purchase.edu FALSE / FALSE 1036259442 ccname
Jeanine

after running either of the cookies5min.asp or cookies5min.php.

In the case of Internet Explorer 6, the cookie file would be:

    ctype     chocolate+chip     sharon.ns.purchase.edu/     1536     1142620928     29526132     2953848224     29526131     *     ccname     Jeanine     sharon.ns.purchase.edu/     1536     1142620928     29526132     2953848224     29526131     *

The values other than the cookie name, value, server, and time (the 1142620928) are used in some way by Internet Explorer and not necessary to decipher.

Session

The following examples show the use of session data. This time, the saved data includes a color for setting the background color (bgcolor) of the Web pages and displaying the time the session began. All of this also could have been done using cookies.

The example uses two scripts for two Web pages. The first presents and handles a form as shown in Figure 13.10.

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Figure 13.10: Form for obtaining information.

After filling in the form, the screen would look like Figure 13.11.

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Figure 13.11: Filled-in form.

After clicking the send info button, you would see the screen shown in Figure 13.12.

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Figure 13.12: Screen showing response.

Notice the form data in the query string shown in the Address field. It contains the form data. The Next page hyperlink is provided to go to the second page. This Web page will make use of the session information. It is shown in Figure 13.13.

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Figure 13.13: Shot of follow-up screen.

Notice the query string in the Address field this time: it contains a rather complex string of letters and numbers that is the session ID. Notice also the color (shade in this black-and-white book) of the page.

The PHP script for the first page ( session1.php) is shown in Table 13.3.

Table 13.3: PHP Script for Setting Session Variables

<?php

Start PHP

if (@($submitted)) {

If test for handler or form

session_start();

Start the session

session_register('cname');

Register the variable named cname as a session variable

session_register('type');

Register type

Session_register('bcolor');

Register bcolor

$starttime = time();

Determine the current time

session_register('starttime');

Register starttime as a session variable

?>

Close PHP

<html><head><title>Use session values </title></head>

Normal HTML

<body>

Normal body

<h1> Welcome

Heading

<?

Re-start PHP

print ("$cname! </h1>\n");

Display form input

print ("<br>You like $type cookies.");

Display form input

?>

End PHP

<a href="session2.php">Next page </a>

Hyperlink to next page

</body>

Body close

</html>

HTML close

<? }

Restart PHP. Close If submitted clause

else { ?>

Else clause. End PHP

<html><head><title>Form for session data </title></head><body>

HTML opening tags

<form action="session1.php">

Form tags

Your name <input type=text name='cname'>

Input tag

<br>

Line break

Your favorite cookie <input type=text name='type'>

Input tag

Your preferred background color <input type=text name='bcolor'>

Input tag

<br>

Line break

<input type=hidden name='submitted' value=TRUE>

Input tag for submitted

<input type=submit value='send info'><input type=reset value='reset'>

Input tag for Submit button

</form>

End form

</body>

End body

</html>

End html

<? } ?>

Restart PHP to close off else clause and then end PHP

The session2.php script is shown in Table 13.4. Note that the session_start function actually re-establishes the session. Any session variables are reinstated with the values set in previous Web pages.

Table 13.4: PHP Script Following Script Setting Session Variables

<? session_start();?>

PHP: re-establish session. End PHP

<html><head><title>Follow on page using session data </title></head>

Normal HTML

<body bgcolor="<?print($bcolor);?>">

Normal HTML. Use session variable to set bgcolor of page

<h1> Welcome to the second page </h1>

Heading

<?

Restart PHP

print ("$cname! </h1>\n");

Display session variable

print ("<br>You like $type cookies.");

Display session variable

print("<br>You began your visit at $starttime");

Display session variable

?><br>

End PHP. Line break

<a href="session3.php">non-existent page </a>

One more link: this is to demonstrate that you could go to yet another page

</body></html>

Ending HTML tags

The time as displayed in the previous scripts is not too meaningful. An improvement would be the following:

    $darray = getdate($starttime);     $dhrs = $darray{"hours"};     $dmins = $darray{"minutes"};     if (strlen($dmins)<2) {$dmins = "0".$dmins;}     print("<br>You began your visit at $dhrs:$dmins");

The if statement is necessary to prevent 2 hours and 5 minutes from appearing as 2:5 when you want 2:05.

The ASP session scripts follow the same format as the PHP scripts. This is one case in which the ASP code is simpler because there is no analog to PHP’s session_start. Since the start time is used here just for display, the code shows the use of the JavaScript date object method toString.

The first ASP script is shown in Table 13.5.

Table 13.5: ASP Script Setting Session Variables

<%@ Language="JavaScript" %>

Set language as JavaScript

<%

Start ASP

var submitted=String(Request("submitted"));

Extract form data

if (submitted != "undefined") {

If test for handler versus form

cname=String(Request("cname"));

Set cname variable from form data

ctype = String(Request("type"));

Set ctype variable from form data

bcolor =String(Request("bcolor"));

Set bcolor data from form data

var starttime = new Date();

Determine current time

Session("cname")=cname;

Set session value for “cname” to be value of cname variable

Session("ctype")=ctype;

Same for ctype

Session("bcolor")=bcolor;

Same for bcolor

Session("starttime")= starttime.toString(); %>

Set session value for “starttime” to be starttime converted to a string End ASP

<html><head><title>Set session values </title></head>

Normal HTML tags

<body>

Body tag

<h1> Welcome

Heading

<%

Restart ASP

Response.Write(cname+"! </h1>\n");

Write out cname

Response.Write("<br>You like "+ ctype+" cookies.");

Write out ctype

%>

End ASP

<a href="session2.asp">Next page </a>

Hyperlink to next page

</body>

Body close

</html>

HTML close

<% }

Restart ASP to close If clause

else { %>

Else clause. End ASP

<html><head><title>Form for session data </title></head><body>

Normal HTML

<form action="session1.asp" method="get">

Form tag

Your name <input type=text name='cname' >

Input tag

<br>

Line break

Your favorite cookie <input type=text name='type' ><br>

Input tag

Your preferred background color <input type=text name='bcolor'>

Input tag

<br>

Line break

<input type='hidden' name='submitted' value=TRUE>

Input tag for hidden variable submitted

<input type='submit' value='send'>

Button

</form>

End form

</body>

End body

</html>

End HTML

<% } %>

Re-open ASP to close Else clause. Close ASP

The session2.asp script that is the next page that makes use of the session information is shown in Table 13.6.

Table 13.6: ASP Script Following Script that Sets Session Variables

<%@ Language="JavaScript" %>

Set JavaScript as language

<%

Start ASP

var bcolor = Session("bcolor");

Extract bcolor from session

var cname = Session("cname");

Extract cname

var ctype = Session("ctype");

Extract ctype

var starttime=Session("starttime");

Extract starttime

%>

End ASP

<html><head><title>Follow on page using session data </title></head>

Normal HTML

<body bgcolor="<%Response.Write (bcolor);%>">

Body tag: break into ASP to get value of bcolor. End ASP

<h1> Welcome to the second page </h1>

Heading

<%

Start ASP

Response.Write(cname+"! </h1>\n");

Write out cname

Response.Write("<br>You like "+ ctype+" cookies.");

Write out ctype

Response.Write("<br>You began your visit at " + starttime);

Write out time

%><br>

End ASP. Line break

<a href="session3.asp">non-existent page </a>

Hyperlink to show you can go to another page

</body></html>

Closing HTML tags




Creating Database Web Applications with PHP and ASP
Creating Database Web Applications with PHP and ASP (Charles River Media Internet & Web Design)
ISBN: 1584502649
EAN: 2147483647
Year: 2005
Pages: 125
Authors: Jeanine Meyer

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