Experiment No (6)

Web server
introduction
A website is a set of related web pages containing content such as text, images, video, audio, etc. A website is hosted on at least
one web server, accessible via a network such as the Internet or a private local area network through an Internet address known
as a Uniform Resource Locator. All publicly accessible websites collectively constitute the World Wide Web.
A webpage is a document, typically written in plain text interspersed with formatting instructions of Hypertext Markup
Language (HTML, XHTML). A webpage may incorporate elements from other websites with suitable markup anchors.
WebPages are accessed and transported with the Hypertext Transfer Protocol (HTTP), which may optionally employ encryption
(HTTP Secure, HTTPS) to provide security and privacy for the user of the webpage content. The user's application, often a web
browser, renders the page content according to its HTML markup instructions onto a display terminal.

HTTP and HTML: Berners-Lee’s Basics

HTTP is a communication standard governing the requests and responses that take place between the browser running on the end
user’s computer and the web server.
The server’s job is to accept a request from the client and attempt to reply to it in a meaningful way, usually by serving up a
requested web page—that’s why the term server is used. The natural counterpart to a server is a client, so that term is applied
both to the web browser and the computer on which it’s running.
Between the client and the server there can be several other devices, such as routers, proxies, gateways, and so on. They serve
different roles in ensuring that the requests and responses are correctly transferred between the client and server. Typically, they
use the Internet to send this information.

The Request/Response Procedure

At its most basic level, the request/response process consists of a web browser asking the web server to send it a web page and
the server sending back the page. The browser then takes care of displaying the page (see Figure 1). These are the steps in the
request and response sequence:
1. You enter http://server.com into your browser’s address bar.
2. Your browser looks up the IP address for server.com.
3. Your browser issues a request for the home page at server.com.
4. The request crosses the Internet and arrives at the server.com web server.
5. The web server, having received the request, looks for the web page on its hard disk.
6. The server retrieves the web page and returns it to the browser.
7. Your browser displays the web page.

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For dynamic web pages, the procedure is a little more involved, because it may bring both PHP and MySQL into the mix (see
Figure 2). Here are the steps:
1. You enter http://server.com into your browser’s address bar.
2. Your browser looks up the IP address for server.com.
3. Your browser issues a request to that address for the web server’s home page.
4. The request crosses the Internet and arrives at the server.com web server.
5. The web server, having received the request, fetches the home page from its hard disk.
6. With the home page now in memory, the web server notices that it is a file incorporating PHP scripting and passes the page to
the PHP interpreter.
7. The PHP interpreter executes the PHP code.

8. Some of the PHP contains MySQL statements, which the PHP interpreter now passes to the MySQL database engine.
9. The MySQL database returns the results of the statements back to the PHP interpreter.
10. The PHP interpreter returns the results of the executed PHP code, along with the results from the MySQL database, to the
web server.
11. The web server returns the page to the requesting client, which displays it.

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PHP and HTML Are Different Languages
It is important to keep in mind that HTML and PHP are two very different languages used for different purposes and executed by
totally different processes. HTML is called a markup language, which combines text with tags to define the structure and
describe the way a document will be displayed. PHP is a programming language that consists of data and instructions and
procedures that tell the computer what operations to perform on the data.

Apache HTTP Server

The Apache HTTP Server, commonly referred to as Apache, is a web server software notable for playing a key role in the initial
growth of the World Wide Web. In 2009 it became the first web server software to surpass the 100 million website milestone.
Apache was the first viable alternative to the Netscape Communications Corporation web server (currently named Oracle iPlanet
Web Server), and since has evolved to dominate other web servers in terms of functionality and performance. Typically Apache
is run on a Unix-like operating system, and was developed for use on Linux.
Apache is developed and maintained by an open community of developers under the auspices of the Apache Software
Foundation. The application is available for a wide variety of operating systems,
including Unix, FreeBSD, Linux, Solaris, Novell NetWare, OS X, Microsoft Windows,OS/2, TPF, and eComStation. Released
under the Apache License, Apache is open-source software.

What Is a WAMP, MAMP, or LAMP?

WAMP, MAMP, and LAMP are abbreviations for “Windows, Apache, MySQL, and PHP,” “Mac, Apache, MySQL, and PHP,”
and “Linux, Apache, MySQL, and PHP,” respectively. These abbreviations describe a fully functioning setup used for
developing dynamic Internet web pages.
WAMPs, MAMPs, and LAMPs come in the form of a package that binds the bundled programs together so that you don’t have
to install and set them up separately. This means you can simply download and install a single program and follow a few easy
prompts to get your web development server up and running in the quickest time with the minimum hassle.

PHP
What is PHP?

 PHP stands for PHP: Hypertext Preprocessor

 PHP is a widely-used, open source scripting language
 PHP scripts are executed on the server
 PHP is free to download and use

What is a PHP File?

 PHP files can contain text, HTML, JavaScript code, and PHP code
 PHP code are executed on the server, and the result is returned to the browser as plain HTML
 PHP files have a default file extension of ".php"

What Can PHP Do?

 PHP can generate dynamic page content

 PHP can create, open, read, write, and close files on the server
 PHP can collect form data
 PHP can send and receive cookies
 PHP can add, delete, modify data in your database
 PHP can restrict users to access some pages on your website
 PHP can encrypt data

With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output
any text, such as XHTML and XML.

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Why PHP?

 PHP runs on different platforms (Windows, Linux, Unix, Mac OS X, etc.)

 PHP is compatible with almost all servers used today (Apache, IIS, etc.)
 PHP has support for a wide range of databases
 PHP is free. Download it from the official PHP resource: www.php.net
 PHP is easy to learn and runs efficiently on the server side

The PHP script is placed between the PHP open tag <?php and the PHP close tag ?>. The code between these two tags is
what the PHP module processes.

EXAMPLE
<?php print "Hello, world"; // This is the C++ style
print "Hello, world"; comment
?> /* This is a C style comment and it can span
multiple lines */
 There are three styles of PHP comments: # And this is a Shell style comment
<?php ?>

variable
A variable is just a storage area. You put things into your storage areas (variables) so that you can use and manipulate them in
your programmes. Things you'll want to store are numbers and text.

In PHP you define a variable with the following form:

 $variable_name = Value;

If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!

Note: Also, variable names are case-sensitive, so use the exact same capitalization when using a variable. The
variables $a_number and $A_numberare different variables in PHP's eyes.

<?php
$hello = "Hello World!";
$a_number = 4;
$anotherNumber = 8;
?>
There are a few rules that you need to follow when choosing a name for yourPHP variables.

 PHP variables must start with a letter or underscore "_".

 PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
 Variables with more than one word should be separated with underscores. $my_variable
 Variables with more than one word can also be distinguished with capitalization. $myVariable.

PHP Variable Scopes

The scope of a variable is the part of the script where the variable can be referenced/used. PHP has four different variable
scopes:

 local
 global
 static
 parameter

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 Local Scope
A variable declared within a PHP function is local and can only be accessed within that function:
Example
<?php echo $x; // local scope
$x=5; // global scope }

function myTest() myTest();

{ ?>
 The script above will not produce any output because the echo statement refers to the local scope variable $x, which has
not been assigned a value within this scope.

You can have local variables with the same name in different functions, because local variables are only recognized by the
function in which they are declared. Local variables are deleted as soon as the function is completed.

Global Scope
A variable that is defined outside of any function, has a global scope. Global variables can be accessed from any part of the
script, EXCEPT from within a function. To access a global variable from within a function, use the global keyword:
Example
<?php
$x=5; // global scope
$y=10; // global scope

function myTest()
{
global $x,$y;
$y=$x+$y;
}

myTest();
echo $y; // outputs 15
?>

PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable. This array
is also accessible from within functions and can be used to update global variables directly. The example above can be rewritten
like this:

Example
<?php
$x=5;
$y=10;

function myTest()
{
$GLOBALS['y']=$GLOBALS['x']+$GLOBALS['y'];
}
myTest();
echo $y;
?>

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Static Scope

When a function is completed, all of its variables are normally deleted. However, sometimes you want a local variable to not be
deleted.

To do this, use the static keyword when you first declare the variable:

Example
<?php
function myTest()
{
static $x=0;
echo $x;
$x++;
}
myTest();
myTest();
myTest();
?>

Then, each time the function is called, that variable will still have the information it contained from the last time the function
was called.

Note: The variable is still local to the function.

Parameter Scope

A parameter is a local variable whose value is passed to the function by the calling code. Parameters are declared in a parameter
list as part of the function declaration:

Example
<?php
function myTest($x)
{
echo $x;
}
myTest(5);
?>

String Variables in PHP

String variables are used for values that contain characters. After we have created a string variable we can manipulate it. A string
can be used directly in a function or it can be stored in a variable. In the example below, we create a string variable called txt,
then we assign the text "Hello world!" to it. Then we write the value of the txt variable to the output:

Example
<?php
$txt="Hello world!";
echo $txt;
?>

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The PHP Concatenation Operator

There is only one string operator in PHP. The concatenation operator (.) is used to join two string values together. The example
below shows how to concatenate two string variables together:

Example
<?php
$txt1="Hello world!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>

The output of the code above will be: Hello world! What a nice day!
The PHP strlen() function

Sometimes it is useful to know the length of a string value. The strlen() function returns the length of a string, in characters. The
example below returns the length of the string "Hello world!":

Example
<?php
echo strlen("Hello world!");
?>
The output of the code above will be: 12
The PHP strpos() function

The strpos() function is used to search for a character or a specific text within a string. If a match is found, it will return the
character position of the first match. If no match is found, it will return FALSE.

The example below searches for the text "world" in the string "Hello world!":

Example
<?php
echo strpos("Hello world!","world");
?> The output of the code above will be: 6.

Tip: The position of the string "world" in the example above is 6. The reason that it is 6 (and not 7), is that the first character
position in the string is 0, and not 1.
String types
PHP supports two types of strings that are denoted by the type of quotation mark that you use. If you wish to assign a literal
string, preserving the exact contents, you should use the single quotation mark (apostrophe), like this:
$info = 'Preface variables with a $ like this: $variable';
In this case, every character within the single-quoted string is assigned to $info. If you had used double quotes, PHP would have
attempted to evaluate $variable as a variable.
On the other hand, when you want to include the value of a variable inside a string, you do so by using a double-quoted string:
echo "There have been $count presidents of the US";

Escaping characters
Sometimes a string needs to contain characters with special meanings that might be interpreted incorrectly. For example, the
following line of code will not work, because the second quotation mark (apostrophe) encountered in the word sister’s will tell
the PHP parser that the end of the string has been reached. Consequently, the rest of the line will be rejected as an error:
$text = 'My sister's car is a Ford'; // Erroneous syntax

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To correct this, you can add a backslash directly before the offending quotation mark to tell PHP to treat the character literally
and not to interpret it:
$text = 'My sister\'s car is a Ford';
Additionally, you can use escape characters to insert various special characters into strings, such as tabs, newlines, and carriage
returns. These are represented, as you might guess, by \t, \n, and \r. Here is an example using tabs to lay out a heading; it is
included here merely to illustrate escapes, because in web pages there are always better ways to
do layout:
$heading = "Date\tName\tPayment";

Multiple-Line Commands
There are times when you need to output quite a lot of text from PHP, and using several echo (or print) statements would be
time-consuming and messy. To overcome this, PHP offers two conveniences. The first is just to put multiple lines between
quotes, as
<?php
$author = "Alfred E Newman";
echo "This is a Headline
This is the first line.
This is the second.
Written by $author.";
?>

PHP also offers a multiline sequence using the <<< operator, commonly referred to as here-document or heredoc for short. This
is a way of specifying a string literal, preserving the line breaks and other whitespace (including indentation) in the text.
<?php
$author = "Alfred E Newman";
echo <<<_END
This is a Headline
This is the first line.
This is the second.
- Written by $author.
_END;
?>
PHP Arithmetic Operators

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PHP Assignment Operators

PHP Incrementing/Decrementing Operators

PHP Comparison Operators

Comparison operators allows you to compare two values:

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PHP Logical Operators

ex:
<?php
$myname = "Brian";
$myage = 37;
echo "a: " . 73 . "<br />"; // Numeric literal
echo "b: " . "Hello" . "<br />"; // String literal
echo "c: " . FALSE . "<br />"; // Constant literal
echo "d: " . $myname . "<br />"; // Variable string literal
echo "e: " . $myage . "<br />"; // Variable numeric literal

?>

PHP Form Handling

The most important thing to notice when dealing with HTML forms and PHP is that any form element in an HTML page
will automatically be available to your PHP scripts.

Example: The example below contains an HTML form with two input fields and a submit button:
<html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>
</body>
</html>

When a user fills out the form above and clicks on the submit button, the form data is sent to a PHP file, called "welcome.php":

"welcome.php" looks like this:

<html>
<body>
Welcome <?php echo $_POST["fname"]; ?>!<br>
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>

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 Output could be something like this:
Welcome John!
You are 28 years old.

Note: The predefined $_GET variable is used to collect values in a form with method="get"

Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and
has limits on the amount of information to send.

Example
<form action="welcome.php" method="get">
Name: <input type="text" name="fname">
Age: <input type="text" name="age">
<input type="submit">
</form>

When the user clicks the "Submit" button, the URL sent to the server could look something like this:

http://www.w3schools.com/welcome.php?fname=Peter&age=37

The PHP $_REQUEST Variable

The predefined $_REQUEST variable contains the contents of both $_GET, $_POST, and $_COOKIE.
The $_REQUEST variable can be used to collect form data sent with both the GET and POST methods.
Example
Welcome <?php echo $_REQUEST["fname"]; ?>!<br>
You are <?php echo $_REQUEST["age"]; ?> years old.

Conditionals
Conditionals alter program flow. They enable you to ask questions about certain things and respond to the answers you get in
different ways. Conditionals are central to dynamic web pages—the goal of using PHP in the first place—because they make it
easy to create different output each time a page is viewed. There are three types of nonlooping conditionals: the if statement, the
switch statement, and the ? operator.

The if Statement
<?php else
if ($bank_balance < 100) {
{ $savings += 50;
$money = 1000; $bank_balance -= 50;
$bank_balance += $money; }
} ?>
$savings += 100;
EX: $bank_balance -= 100;
<?php }
if ($bank_balance < 100) else
{ {
$money = 1000; $savings += 50;
$bank_balance += $money; $bank_balance -= 50;
} }
elseif ($bank_balance > 200) ?>
{
The switch Statement
<?php
switch ($page)
{
case "Home":

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echo "You selected Home";
break;
case "About":
echo "You selected About";
break;
case "News":
echo "You selected News";
break;
case "Login":
echo "You selected Login";
break;
case "Links":
echo "You selected Links";
break;
}
?>
PHP Loops
Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost
equal lines in a script we can use loops to perform a task like this.
In PHP, we have the following looping statements:

while - loops through a block of code while a specified condition is true

do...while - loops through a block of code once, and then repeats the loop as long as a specified condition is true
for - loops through a block of code a specified number of times
foreach - loops through a block of code for each element in an array

The while Loop

The while loop executes a block of code while a condition is true.
Syntax
while (condition)
{
code to be executed;
}
Example
The example below first sets a variable i to 1 ($i=1;). Then, the while loop will continue to run as long as i is less than, or equal to
5. i will increase by 1 each time the loop runs:
<html>
<body>

<?php
$i=1;
while($i<=5)
{
echo "The number is " . $i . "<br>";
$i++;
}
?>
</body>
</html>

Output:
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

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The do...while Statement
The do...while statement will always execute the block of code once, it will then check the condition, and repeat the loop while the
condition is true.
Syntax
do
{
code to be executed;
}
while (condition);

Example
<html>
<body>
<?php
$i=1;
do
{
$i++;
echo "The number is " . $i . "<br>";
}
while ($i<=5);
?>
</body>
</html>
Output:
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6

The for Loop

The for loop is used when you know in advance how many times the script should run.
Syntax
for (init; condition; increment)
{
code to be executed;
}
Parameters:
init: Mostly used to set a counter (but can be any code to be executed once at the beginning of the loop)
condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
increment: Mostly used to increment a counter (but can be any code to be executed at the end of the iteration)
Note: The init and increment parameters above can be empty or have multiple expressions (separated by commas).
Example
<html> </body>
<body> </html>
<?php
for ($i=1; $i<=5; $i++) Output:
{ The number is 1
echo "The number is " . $i . "<br>"; The number is 2
} The number is 3
?> The number is 4
The number is 5

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EX:
<html>
<head>
<title>Font Choices</title>
</head>
<body>
<center>
<h1>Font Choices</h1>
<h3>Demonstrates how to read HTML form elements</h3>

<form method = "post"

action = "borderMaker.php">

<h3>Text to modify</h3>
<textarea name = "basicText"
rows = "10"
cols = "40">
software engineering is “A discipline whose aim is the production of quality software, software that is delivered on time, within
budget, and that satisfies its requirements”.</textarea>

<table border = 2>

<tr>
<td><h3>Border style</h3></td>
<td colspan = 2><h3>Border Size</h3></td>
</tr>
<tr>
<td>
<select name = borderStyle>
<option value = "ridge">ridge</option>
<option value = "groove">groove</option>
<option value = "double">double</option>
<option value = "inset">inset</option>
<option value = "outset">outset</option>
</select>
</td>
<td>

<select size = 5 name = borderSize>

<option value = "1">1</option>
<option value = "2">2</option>
<option value = "3">3</option>
<option value = "5">5</option>
<option value = "10">10</option>
</select>
</td>

<td>
<input type = "radio"
name = "sizeType"
value = "px">pixels<br>
<input type = "radio"
name = "sizeType"
value = "pt">points<br>
<input type = "radio"
name = "sizeType"
value = "cm">centimeters<br>

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<input type = "radio"
name = "sizeType"
value = "in">inches<br>
</td>
</tr>
</table>

<input type = "submit"

value = "show me">

</form>
</center>
</body>
</html>

borderMaker.php
<html> border-style:$y;
<head> border-color:green"
<title>Your Output</title> HERE;
</head>
<body> print "<div style = $theStyle>";
<h1>Your Output</h1> print $_post["basicText";
<center> print "</span>";
<?
$x=$_post["borderSize$sizeType"]; ?>
$y=$_post["borderStyle"]; </center>
$theStyle = <<<HERE </body>
"border-width:$; </html>

Assignment
design the following web page, if user typing the correct name and password then the page will be
forwarded to another web page otherwise a message contains "wrong username or password" will appear.

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