Client side & Server side scripting and
Introduction to PHP
Server side scripting
Server-side scripting is a method of programming for the
web that runs software on the server rather than the browser
or installed plugins to create dynamic web pages.
Languages used for these tasks are normal programming
languages which include Perl, PHP, JSP, Ruby, ColdFusion,
and Python
What can server scripts do?
Customize a web page and dynamically change its contents
Respond to queries from users or from HTML forms
Access database and send the information back to the
browser
Client side scripting language
Client-side scripts are placed within an HTML document in the user’s
web browser rather than the web server to allow greater interactivity in a
document.
For example – client-side scripting could check the user’s form for errors
before submitting it
Enables web pages to change content according to user input and other
variables.
Can also be stored in a separate file that is referenced to the documents
that use it.
How does it work
Usually, JavaScript code starts with the tag <script language="JavaScript">
and ends with the tag </script>.
Files are first sent to the user’s computer by the web server which executes
the script and displays the document.
The client-side script may also include browser directions based on certain
user functions such as clicking buttons.
Frequently, you can see the source code by viewing the file that contains
the script.
PHP Introduction
PHP is a recursive acronym for “PHP: Hypertext Preprocessor” –
It is a widely-used open source general-purpose scripting language that is
especially suited for web development and can be embedded into HTML.
PHP Introduction
PHP is a server-side scripting language
PHP scripts are executed on the server
PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid,
PostgreSQL, Generic ODBC, etc.)
PHP is open source software-
PHP is free to download and use
PHP Introduction
PHP runs on different platforms (Windows, Linux, Unix, etc.)
PHP is compatible with almost all servers used today (Apache, IIS, etc.)
PHP is FREE to download from the official PHP resource: www.php.net
PHP is easy to learn and runs efficiently on the server side
PHP Introduction
The PHP code is enclosed in special start and end processing instructions <?
php and ?> that allow you to jump into and out of "PHP mode."
PHP Introduction
PHP Introduction
PHP code is executed on the server, generating HTML which is then sent to
the client.
The client would receive the results of running that script, but would not know
what the underlying code was.
PHP Introduction
PHP Getting Started
On windows, you can download and install XAMP. With one installation and
you get an Apache webserver, database server and php.
On mac, you can download and install MAMP.
http://www.mamp.info/en/index.html
PHP Hello World
Above is the PHP source code.
PHP Hello World
It renders as HTML that looks like this:
PHP Comments
InPHP, we use // to make a single-line
comment or /* and */ to make a large
comment block.
Php Variables
Rules for PHP variables:
A variable starts with the $ sign, followed by the name of the variable
A variable name must start with a letter or the underscore character
A variable name cannot start with a number
A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9,
and _ )
Variable names are case-sensitive ($age and $AGE are two different variables)
<!DOCTYPE html>
<html>
<body>
<?php
$x = 5;
$y = "John";
echo $x;
echo "<br>";
echo $y;
?>
</body>
</html
<!DOCTYPE html>
<html>
<body>
<?php
$txt = "W3Schools.com";
echo " $txt!";
?>
</body>
</html>
Type of the variable
<!DOCTYPE html>
<html>
<body>
<?php
$x = 5;
var_dump($x);
?>
</body>
</html>
OUTPUT: int(5)
Assigning multiple values
<!DOCTYPE html>
<html>
<body>
<?php
$x = $y = $z = "Fruit";
echo $x;
echo $y;
echo $z;
?>
</body>
</html>
Conditional statements:
If else
<?php
if (5 > 3) {
echo "Have a good day!";
}
?>
OUTPUT: Have a good day
Switch
<!DOCTYPE html>
<html>
<body>
<?php
$favcolor = "red";
switch ($favcolor) {
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, nor green!";
}
?>
</body>
PHP Loops
In PHP, we have the following loop types:
while - loops through a block of code as long as the specified
condition is true
do...while - loops through a block of code once, and then
repeats the loop as long as the 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
While loop
<!DOCTYPE html>
<html>
<body>
<?php
$i = 1;
while ($i < 6) {
echo $i;
$i++;
}
?>
</body>
</html>
OUPTUT: 12345
<!DOCTYPE html>
<html>
<body>
<?php
$i = 1;
while ($i < 6) {
if ($i == 3) break;
echo $i;
$i++;
}
?>
</body>
</html>
do while
<!DOCTYPE html>
<html>
<body>
<?php
$i = 1;
do {
echo $i;
$i++;
} while ($i < 6);
?>
</body>
</html>
OUTPUT: 12345
For loop
for (expression1, expression2, expression3) {
// code block
}
<!DOCTYPE html>
<html>
<body>
<?php
for ($x = 0; $x <= 10; $x++) {
echo "The number is: $x <br>";
}
?>
</body>
</html>
foreach loop
<!DOCTYPE html>
<html>
<body>
<?php
$colors = array("red", "green", "blue", "yellow");
foreach ($colors as $x) {
echo "$x <br>";
}
?>
</body>
</html>
<!DOCTYPE html>
<html>
<body>
<?php
$members = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
foreach ($members as $x => $y) {
echo "$x : $y <br>";
}
?>
</body>
</html>
Php functions
<!DOCTYPE html>
<html>
<body>
<?php
function myMessage() {
echo "Hello world!";
}
myMessage();
?>
</body>
</html>
OUTPUT: Hello world!
Function arguments
<!DOCTYPE html>
<html>
<body>
<?php
function familyName($fname) {
echo "$fname joy.<br>";
}
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai Jim");
familyName("Alex");
?>
</body>
</html>
Arrays
An array is a special variable that can hold many values under a single
name, and you can access the values by referring to an index number or
name.
In PHP, there are three types of arrays:
Indexed arrays - Arrays with a numeric index
Associative arrays - Arrays with named keys
Multidimensional arrays - Arrays containing one or more arrays
Create array
You can create arrays by using the array() function:
<?php
$cars = array("Volvo", "BMW", "Toyota");
//$cars = ["Volvo", "BMW", "Toyota"];
var_dump($cars);
?>
Output: array(3) {
[0]=>
string(5) "Volvo"
[1]=>
string(3) "BMW"
[2]=>
string(6) "Toyota“}
Php form handling
The PHP superglobals $_GET and $_POST are used to collect
form-data.
<form action="welcome.php" method="post">
Name: <input type="text" name="name"><br>
E-mail: <input type="text" name="email"><br>
<input type="submit">
</form>
Welcome.php
<html>
<body>
Welcome
<?php echo $_POST["name"]; ?><br> // echo $_GET["name"];
Your email address is: <?php echo $_POST["email"]; ?>
</body>
</html>
GET vs POST
Both GET and POST create an array (e.g. array( key1 => value1,
key2 => value2, key3 => value3, ...)).
This array holds key/value pairs, where keys are the names of the
form controls and values are the input data from the user.
$_GET is an array of variables passed to the current script via
the URL parameters.
$_POST is an array of variables passed to the current script via
the HTTP POST method.
<form method="post" action="<?php echo
htmlspecialchars($_SERVER["PHP_SELF"]);?>">
When the form is submitted, the form data is sent with
method="post".
The $_SERVER["PHP_SELF"] is a super global variable that
returns the filename of the currently executing script.
So, the $_SERVER["PHP_SELF"] sends the submitted form data to
the page itself, instead of jumping to a different page.
The user will get error messages on the same page as the form
The htmlspecialchars() function converts special characters into
HTML entities.
This means that it will replace HTML characters like < and > with
< and >. This prevents attackers from exploiting the code by
injecting HTML or Javascript code (Cross-site Scripting attacks) in
forms.
The test_input() function is a custom function created in this script to
sanitize input data received from the user. Here's what each step in the
function does:
trim($data): Removes any leading or trailing whitespace from the input
data. This ensures that there are no unintentional spaces at the beginning or
end of the input.
stripslashes($data): Removes any backslashes (\) from the input data.
Backslashes are often used to escape special characters in strings, but they
can sometimes cause unintended behavior if not handled properly.
htmlspecialchars($data): Converts special characters in the input data to
their corresponding HTML entities. This step helps prevent cross-site
scripting (XSS) attacks by ensuring that user input is displayed as text rather
than interpreted as HTML code.
