A server is a computer or a device that provides functionalities for other programs of devices called "Client".

(i) Variable name must always begin with a \($\) symbol.
(ii) Variable name can not start with a number.
(iii) Variable names are case-sensitive. Eg. \($\)a = 6;

Uniform Resource Locater (URL), refers the address of a specific web page or file on the internet.

(i) Webserver is software which is running in server hardware.
(ii) It takes the responsibilities for compilation and execution of server side scripting languages.

(i) PHP can be easily embed with HTML and other client side scripting language like CSS [cascading style sheets) and Java scripts.
(ii) It also creates dynamic and interactive webpages in the real time Web development projects.
(iii) It is competitor of ASP and JSP.
(iv) 78.9% of websites are developed by PHP.

Operator is a symbol which is used to perform mathematical and logical operations in the programming languages.
Different types of operators in PHP are:
(i) Arithmetic operators
(ii) Assignment operators
(iii) Comparison operators
(iv) Increment/Decrement operators.
(v) Logical operators and
(vi) String operators
1. Arithmetic operators perform arithmetical operations such as addition, subtraction, multiplication and division etc.
2. Assignment operators are performed with numeric values to store a value in a variable. Default assignment operator is "="
3. Comparison operators perform an action to compare two values.
4. Increment/Decrement operators are used to perform increasing (or) decreasing variable's value.
5. Logical operators are used to combine conditional statements.
6. String operators are two operators which are used to perform string related operations such as concatenation and concatenation assignment.

(i) Server side scripting languages is used in web development.
(ii) It is alternative for web server and itself to deliver a static web page.
(iii) It is used to provide customized interface for the user.
(iv) It also enables the website owner to hide the source code.

An operator is a symbol that performs a given action on a value or group of values. The values the operation is performed upon are known as operands.
The types of operators in PHP are
(i) Arithmetic operators
(ii) Assignment operators
(iii) Comparison operators
(iv) Increment/Decrement operators
(v) Logical operators and
(vi) String operators
1. Arithmetic operators
Arithmetic operators are used to perform math operations, for example, addition, subtraction, multiplication, and division.

2. Assignment operators
The assignment operator is used to assign a value to a variable. The assignment operator takes the value of its right-hand operand and assigns it to its left-hand operand.

3. Comparison operators
Comparison operators are used to compare two values and determine whether a certain condition is true or false.

4.Logical Operators:
Logical operators are used to perform logical operations on variables and values.

5. Increment and Decrement operators
In PHP, the increment operator ++ is used to increase the value of a variable by 1, and the decrement operator is used to decrease the value of a variable by 1. The increment and decrement operators can be used as either prefix or postfix operators.

6. String operator

String operators have concatenation operator(.) and concatenation assignment operator(-). Concatenation means adding one or more variables to an existing variable.

The following are the steps to install and configure Apache Httpd webserver and PHP module in windows server machine.
Step 1:
Go to Apache foundation website and download the Httpd webserver software.
https://httpd.apache.org/download.cgi.
Step 2:
After downloading MSI file from Apache foundation website, user launches the MSI file and clicks next.
Click on next and next button finish the installation on server machine.
Software takes default port number 130 or 130130.
Once the user finished, webserver software is installed and configured on server hardware machine as a service.
Step 3:
To test the installation of Apache Httpd webserver, enter the following URL. from your web browser which is installed in your client machine.
https://localhost:130/ (or) https://localhost:130130
The output page that says "Its works"
Step 4:
Administrator user can start, stop and restart the webserver service at any time via windows control panel.
Once the services stops, the client machine will not receive the response message from server machine.
Step 5.
Webserver's configuration setting file "httpd.conf" is located in the conf directory under the apache installation directory.
Edit this file and enable the PHP module to run PHP scripting language.

Client side scripting language:
1. Code that is present in a client's HTML page.
2. The language used for client scripting is Java script. It is the most widely used language for client-side scripting.
3. It is compatible and has the ability to run on any browsers.
4. The browser then downloads that code temporarily and processes it without the server.
5. As a result, it is now faster and easier to do client side scripting and leaving less word for the server.
Server side scripting language:
1. Server side scripting usually happens on the back-end of a website.
2. Server side scripting creates a path for the website to the database and all behind the scene work which organizes and runs a website. In server side scripting, the responses can be customized based on requirement of the user.
3. Example of server side programming language is PHP scripting language.
4. It can be executed via an interpreter which is installed in the webservers or CGI (Common Gateway Interface).
5. The most of the webservers such as Apache Tomcat, Microsoft IIS (Internet Information Server) supports the PHP interpreter module.