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Unformatted text preview: COMP 3322B
Modern Technologies on
World Wide Web
2nd semester 2018-2019
PHP - Part I (O2) Dr. C Wu
Department of Computer Science
The University of Hong Kong What we are going to learn next Technologies for creating dynamic, interactive web pages
PHP [server side]
JavaScript (AJAX, JSON, jQuery) [client side]
HTML5 [client side]
Node.js [server side and client side]
AngularJS [client side]
React [client side] PHP basics
PHP stands for hypertext preprocessor
PHP is a server-side scripting language, executed on the server
PHP files can contain text, HTML, CSS, JavaScript, and PHP script
PHP files are returned to the browser as HTML documents
PHP files have a file extension of ".php" Widely used for making dynamic and interactive web pages
PHP runs efficiently on different platforms (Windows, Linux, Unix, etc.)
PHP is compatible with almost all servers used today (Apache, IIS,
etc.) PHP syntax
A PHP script can be placed anywhere in the document
A PHP script starts with <?php and ends with ?>
On servers with shorthand support (set short_open_tag=on in
php.info), a PHP script can start with <? and end with ?>
echo 'Welcome '.($user['is_logged_in'] ? $user['first_name'] : 'Guest').'!'; Each code line in PHP script must end with a semicolon
example
<html>
<body>
<?php
echo "Hello World";
?>
</body>
</html> two basic statements
to output text and
variables: echo and
print. PHP variables
Variables start with $, followed by the name of the variable
The variable name must begin with a letter or _
A variable name can only contain alpha-numeric characters and
underscores (A-z, 0-9, and _ )
Variable names are case sensitive
A variable is created the moment you first assign a value to it:
$myCar="Volvo"; If you create/use a variable without
assigning it a value, then it has the
value of null. a variable does not need to be declared before assigning a value to it
we do not have to tell PHP which data type the variable is
PHP automatically converts the variable to the correct data type,
depending on its value PHP variables (cont’d)
Main PHP data types
string (enclosed in single or double quotes),
integer, float, boolean, null,
array:
<?php $cars = array("Volvo", "BMW", "Toyota"); echo $cars[0]; ?> <?php $colors = array("Peter"=>"red", "Joe"=>"blue", "Amy"=>"pink"); echo $colors['Peter']; ?> indexed array object: associative array <?php class Movie { func3on Movie() { $this->name = "Mission Impossible"; } } $mymovie = new Movie(); echo $mymovie->name; ?> key can be integer and string;
value can be of any type PHP variables (cont’d)
Some special predefined variables (superglobals)
$_GET, an associative array containing variables and values
sent from the client with the get method
$_POST, an associative array containing variables and values
sent from the client with the post method
$_COOKIE, an associative array containing cookie variables
and values
$_SESSION, an associative array containing session variables
and values PHP statements, operators and function
PHP supports a number of statements (If/Else, Switch,
While, For, etc.) and operators (+, - , * , /, etc.)
check out for details
not case sensitive PHP supports functions
PHP provides more than 1000 built-in functions
hUp://php.net/manual/en/indexes.func3ons.php <?php or we define our own functions: . is string concatena3on operator in PHP func3on concat($str, $num) { return $str.$num; } echo concat("I am No. ", 1); ?> Case sensitivity in PHP
Case sensitive
variables
constants
array keys
class properties Case insensitive
function names
class contructors/methods
keywords and constructs (e.g., if, else, echo, etc.) PHP server-side processing How to retrieve client-side input data?
How to perform server-side computation?
How to keep the state information of a client across
different pages he/she accessed?
How to store information permanently on the server? Two methods to send data to server
HTTP'Request'message'format'
Request'line' HTTP
GET and
POSTrequest Header' HTTP'R
Blank'line' Data can be sent to the server through two methods HTTP request
Request$line' HTTP'Request'message'format'
Body' GET
– pass
data data
along along
in the URL.
GET:
pass
in the URL Request'line' Request'
HTTP''
as_sitesearch=hku.hk
URL'
Request line
method' version' Header' Variable name : q
space'Value : computer Variable name : hl
as_sitesearch
space'
\r\n'
Value : hku.hk
en
HTTP''
Blank'line' Request'
URL'
POST – pass
data
in
the
GET'''/~c0322/test/index.html'''HTTP/1.1'
version'
POST: method'
pass data in the body of HTTP request
y
g
p
Try
to
change
“computer”
body of HTTP request.
request
space'
space'
\r\n'
Example'
to “apple”,
or change “en”
GET'''/~cwu/c0322/index.html'''HTTP/1.1'
to “zh TW” to see
Example'
different pages generated q=computer&as_sitesearc
h=hku.hk Body' GET
Two typical cases where GET is used to send data to server
Case 1. Submit an HTML <form>, with form attribute method ="get”; the data
entered into the form will be appended to the end of the url (specified in the action
attribute) in name/value pairs Example
<form action=" ; method="get">
<fieldset>
<legend>Search String</legend>
<input type="text" name="q">
<input type="hidden" name="as_sitesearch" value="hku.hk">
</fieldset>
<input type="submit" value=“Site Search”>
</form>
yoursearchstring URL in the GET request generated after clicking submit button:
GET
Case 2. Click a hyperlink on an HTML page, with variable and value
appended at the end of the target URL
Example
<p>Click your favourite breakfast recipe below: </p> <ul> <li><a href="hUp:// toast</a></li> <li><a href=“hUp:// tart</a></li> <li><a href=“hUp:// prata</a></li> </ul> Screenshot Example 1 (login.html)
A login <form> using the GET method <!DOCTYPE html> <html> <head> <3tle>Login page</3tle> </head> <body> <form ac3on="processLogin.php" method="get"> Login name <input type="text" name="loginName"><br> Password <input type="password" name="loginPassword"><br> <input type="submit"> </form> </body> </html> login.html Browser display of login.html Example 1 (processLogin.php)
php)
(processLogin.php)
When the <form> isExample
submitted, the 1 (processLogin
cwu ***** browser sends an HTTP GET request to
Login
<form>
using GET method.
method
retrieve the page specified
in the
action
attribute (i.e., processLogin.php),
When the <form>and
is submitted
appends the variable names
and values at
When the <form> with method = “get” is
the end of the requested url
submitted, the browser will send an HTTP request Browser display of Browser display of login.html
login.html
to retrieve the page specified in the <form> action
(i.e., processLogin.php). The browser will append the variable names and
values at the end of the requested page. 9 Example 1 (processLogin
php)
(processLogin.php)
Login <form> using GET method.
method
When the <form> is submitted
When the <form> with method = “get” is
submitted, the browser will send an HTTP request
to retrieve the page specified in the <form> action
(i.e., processLogin.php). Browser display of login.html The browser will append the variable names and
values at the end of the requested page. GET /~c0322/processLogin.php?loginName=cwu&loginPassword=12345 HTTP/1.1 Host : i.cs.hku.hk User-Agent : Mozilla/5.0 …… 9 Example 1 (processLogin.php) Example 1 (processLogin.php)
Access the “GET” data on server side
<!DOCTYPE html> <html> <head> <3tle>Process Login</3tle> </head> <body> <? print "<p>".$_GET['loginName']."</p>"; print "<p>".$_GET['loginPassword']."</p>"; ?> </body> </html> processLogin.php $_GET['variableName'] can access the variable passed by GET method HTML was designed to display data; XM
transport and store data. Example 1 (client-server interaction)
HTTP request GET /~c0322/processLogin.php?loginName=cwu&loginPassword=12345 …
HTTP$request$(URL,$e.g.$h3p:// file.jsp?te Client$(web$browser)$ HTTP response Web$server$ HTTP/1.1 200 OK …. <!DOCTYPE html> <html> <head> <3tle>Process Login</3tle> </head> <body> <p>cwu</p> <p>12345</p> </body> </html> A
Run PHP script and p
output HTML
c
u
P
In Disadvantages of the GET method Limit on variable lengths: many servers put an
upper limit on how many characters you can put in
the URL
Security issue: information that you fill in the
<form>, including the masked password field,
becomes visible in the URL when you submit the
form POST The POST method sends your data to the server
through the body part in an HTTP request
The information in your <form> won't appear in the URL
Usually a larger upper limit is put on the number of bytes
that can be transmitted via the POST method Example 2 (login.html)
A login <form> using the POST method <!DOCTYPE html> <html> <head> <3tle>Login page</3tle> </head> <body> <form ac3on="processLogin.php" method="post"> Login name <input type="text" name="loginName"><br> Password <input type="password" name="loginPassword"><br> <input type="submit"> </form> </body> </html> login.html Browser display of login.html Example 2 (processLogin.php) Example 1 cwu
When the <form> is submitted, the
(processLogin
php)
(processLogin.php)
*****
browser sends an HTTP POST request to
retrieve the page specified in the action
Login <form> using GET method.
method
attribute (i.e., processLogin.php), and
When the
<form>
is submitted
the variable names and values
are
sent
in
When the <form>
with method = “get” is
the body part of the HTTP POST
request
Browser display of submitted, the browser will send an HTTP request
message
to retrieve the page specified in the <form> action login.html
Browser display of login.html (i.e., processLogin.php).
The browser will append the variable names and
values at the end of the requested page. 9 Example 2 (processLogin.php)
POST /~c0322/processLogin.php HTTP/1.1 Host : i.cs.hku.hk User-Agent : Mozilla/5.0 ..... Content-Type: applica3on/x-www-form-urlencoded Content-Length: 33 The browser will append the variable names and
values at the end of the requested page.
When the <form> with method = “get” is
submitted, the browser will send an HTTP request
to retrieve the page specified in the <form> action
(i.e., processLogin.php). 9 loginName=cwu&loginPassword=56789 default content type when
sending form data using post:
encoding key/value pairs using
URL encoding on nonalphanumeric characters
(
html/html_urlencode.asp) Browser display of login.html When the <form> is submitted Login <form> using GET method.
method Example 1 (processLogin
php)
(processLogin.php) Example 2 (processLogin.php)
Access the “POST” data on server side
<!DOCTYPE html> <html> <head> <3tle>Process Login</3tle> </head> <body> <? print "<p>".$_POST['loginName']."</p>"; print "<p>".$_POST['loginPassword']."</p>"; ?> </body> </html> processLogin.php $_POST['variableName'] can access the variable passed by POST method Server-side computation using PHP Client side does not know about the processing on the
server side; only the generated html page will be sent to
the client side Example 3 (processLogin.php) Example 3 (processLogin.php)
(processLogin php) <!DOCTYPE HTML PUBLIC " //W3C//DTD HTML 4.01 Transitional//EN"
<!DOCTYPE html>
" ;
p
g
<html>
<head>
String array variable
<title>Process Login</title>
</head>
Note that
h PHP variables
bl are dynamically
d
dynamic typed,
d
typed
<body>
<?
if we use 'single quote' or "double quote"
$user_name[0]="Kit";
to indicate the value of a variable, the
$user_password[0]='password';
variable is regarded as string automatically.
automatically
$user_account_balance[0]= 1000;
$user_name[1]="Bobby";
$user_password[1]="password2";
$user_account_balance[1]= 2000; PHP array is very flexible!
g or a string.
g
The keyy can either be an integer
The value can be of any type. $user_name[2]="Harry";
$user_password[2]="password3";
$user_account_balance[2]= 3000;
17 Example 3 Example 3 (processLogin.php)
(processLogin php)
(processLogin.php) <!DOCTYPE HTML PUBLIC " //W3C//DTD HTML 4.01 Transitional//EN"
<!DOCTYPE html>
" ;
p
g
<html>
<head>
Integer array variable
<title>Process Login</title>
</head>
The
h $user_account_balance
$
b l
variable
bl is an
<body>
<?
array variable.
$user_name[0]="Kit";
$user_password[0]='password';
$user_account_balance[0]
$user account balance[0] stores an integer
$user_account_balance[0]= 1000; value $user_name[1]="Bobby";
$user_password[1]="password2";
$user_account_balance[1]= 2000;
$user_name[2]="Harry";
$user_password[2]="password3";
$user_account_balance[2]= 3000; … 18 Example 4 (processLogin.php)
(processLogin php) Example 3 (processLogin.php) …
if (in
(in_array($_POST[
array($ POST["loginName"]
loginName ],$user_name)){
$user name)){ in_array()
}else{
print "No such user!";
} in_array() – The in_array()
function checks if a value exists
in an array 24 Example 4 (processLogin.php)
(processLogin php) Example 3 (processLogin.php) …
if (in
(in_array($_POST[
array($ POST["loginName"]
loginName ],$user_name)){
$user name)){
$key = array_search($_POST["loginName"], $user_name); array_search()
}else{
print "No such user!";
} array_search()
array
search() – The
array_search() function searches
the array for a given value and
returns the corresponding key.
key 25 Example 3 (processLogin.php) Example 4 (processLogin.php)
(processLogin php)
… Now we know how to
if (in
(in_array($_POST[
array($ POST["loginName"]
loginName ],$user_name)){
$user name)){
perform
f
server side
id
$key = array_search($_POST["loginName"], $user_name);
if ($user_password[$key] == $_POST["loginPassword"]){
processing, but every
print "Login correct!<br>";
time
we reload
Browser display of print "Name
Name :"
: .$user_name[$key].
$user name[$key] "<br>";
<br> ;
processLogin.php when print "Account balance:".$user_account_balance [$key].'<br>'; login.php
we are
[$key]."<br>";
login is successful asked to login again.
}else
print "Login
Login fail!";
fail! ;
Question:
}else{
How to make the
print "No such user!";
}
server remember the
'login.html'>Back to login page</a>"; print "<br><a
<br><a href
href='login.php'>Back
login.php
>Back to login page</a>";
page</a> ;
l i information
login
i f
i off
?>
</body>
each client?
</html> 26 References
PHP tutorial:
PHP project page: ...
View
Full Document
- Fall '13
- Dr. C. Wu
- Computer Science, Hypertext Transfer Protocol, Volvo, CWU
