Bài giảng Web technologies and e-Services - Bài 11: Maintaining state through multiple forms - Trường Đại học Bách khoa Hà Nội
Maintaining state through
multiple forms
HTTP – stateless protocol
HTTP is a stateless protocol
àOnce a web server
completes a client's request
for a web page, the
connection between the two
goes away.
àThere is no way for a
server to recognize that a
sequence of requests all
originate from the same
client.
2
What Are Multiple-Form Web Sessions?
• A multiple-form Web session leads the user through
a series of HTML forms that work together and pass
data from form to form.
• E.g.
• To build a shopping cart or on-line survey.
• To save user authentication information from page to
page
• To store persistent user preferences on a site
3
Example Multiple Screen Session
4
How to maintain the state through
multiform?
• Use tricks to keep track of state information
between requests (session tracking)
• Using hidden form fields
• URL rewriting: every local URL on which the user might
click is dynamically modified to include extra
information
• Using cookies: a bit of information that the server give to
a client à depends on the client
• Using session
5
Content
2. User browser cookies
3. PHP session
6
1. Hidden fields
• Hidden fields are part of HTML forms
• Not displayed but value can be accessed in receiving
script like any other variable.
7
A Full Script Example
• Consider an example script sets a hidden field
• Implements the Order Info form
• on submit sends data to order2.php
8
PHP Script – order.html
1. <html><head><title>Order Product</title></head><body>
2. <form action="order2.php“ method="post">
3. <h1> Hardware Product Order Form</h1>
4. <br><p class="highlight">
5. We have hammers, handsaws, and wrenches on special
today!
6. </p>
7. <input type="hidden" name="sample_hidden"
value="Welcome!">
8. <br>Enter Item: <input text type="text" size="15”
maxlength="20" name="product">
9. Enter Quantity: <input text type="text" size="15”
maxlength="20" name="quantity"><br>
10. <br><input type="submit" value="Click To Submit">
11. <input type = "reset" value="Reset">
12. </form></body></html>
9
The Output ...
The previous code can be executed at
10
Receiving Hidden Fields in
Web Sessions
• Your scripts can receive data from hidden fields like
any other data.
• Suppose the following is stored at: order2.php
1. <html><head><title> Order Product 2 </title> </head>
2. <body>
3. <form action=“order3.php“ method="post">
4. <?php $sample_hidden = $_POST[“sample_hidden”];
5. $product = $_POST[“product”]; $quantity =
$_POST[“quantity”];
6. print "<p class=“highlight”>";
7. print "Hidden value=$sample_hidden </p><br>";
8. print "You selected product=$product and
quantity=$quantity";
11
Receiving PHP Script
9. print "<br><br><input type=\"hidden\" name=\"product\“
value=\"$product\"> ";
10. print "<input type=\"hidden\" name=\"quantity\“
value=\"$quantity\">";
11. print "<input type=\"hidden\"
name=\"sample_hidden\"value=\"$sample_hidden\">";
12. print 'Please enter your name:';
13. print '<input type="text" size="15" maxlength="20“
name="name">';
14. print ' and billing code: (5 digits)';
15. print '<input type="text" size="5" maxlength="5"
name="code">';
16. print '<br> <input type=submit value="Process Order">';
17. print '<input type=reset>';
18. ?></form></body></html>
12
Sending email from PHP scripts
• Sometimes it is useful to send email from a PHP script:
• PHP uses mail() that by default sends e-mail via the Simple
Mail Transfer Protocol (SMTP).
mail(to_address, subject, message, extra_headers);
Specify the
Text of the email
Specify the
destination email
address.
Specify the subject line
of the e-mail.
Specify additional
email headers.
13
Consider the following
example …
1. $dest='orders@hardwareville.com';
2. $subject = 'New Hardware Order';
3. $message = 'Enclosed is a new order for 12
hammers.\n Thanks.';
4. $extra = 'From: harry@hardwareville.com';
5. mail( $dest, $subject, $message, $extra );
14
Consider the following full
example …
• Implements save and notify
• Called from order2.php and saved at order3.php
• Can access variables $product, $quantity, and
$sample_hidden sent as hidden fields from the
Billing Info form.
15
The following PHP Script …
1. <html><head><title>Order Product 3</title> </head><body>
2. <?php
3. $sample_hidden = $_POST[“sample_hidden”];
quantity=$_POST[“$quantity”];
4. $product = $_POST[“product”]; $name=$_POST[“name”];
5. $email='orders@hardwareville.com';
6. $body = "New Order: Product=$product Number=$quantity Cust=$name
Code=$code";
7. print '<font size=4>';
8. print "<br>Sending e-mail to order handling department at $email
... </font>";
9. print "<br>The e-mail body is <i>: $body. </i>";
10. $from = 'harry@hardwareville.com';
11. $subject = "New order from $name";
12. mail($email, $subject, $body, "From: $from");
13. print '<br><font color="blue"> E-mail sent. Thanks for
ordering. </font>';
14. print "<br>By the way, sample hidden=$sample_hidden";
15. ?></body></html>
16
Would have the following
output …
17
Would have the following
output …
18
Content
1. Hidden fields
3. PHP session
19
Using Browser Cookies …
• Cookies are small pieces of data that a Web
application can save when a user visits the Web
page.
• Stored on the visitor’s hard drive
• a Web page script can read the previously stored browser
cookie data
20
Tải về để xem bản đầy đủ
40 trang
27/04/2022
9080
Bạn đang xem 20 trang mẫu của tài liệu "Bài giảng Web technologies and e-Services - Bài 11: Maintaining state through multiple forms - Trường Đại học Bách khoa Hà Nội", để tải tài liệu gốc về máy hãy click vào nút Download ở trên
File đính kèm:
- bai_giang_web_technologies_and_e_services_bai_11_maintaining.pdf
