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

A server is a computer or a device that provides functionality for other programs or devices, called "clients". This architecture is called the client server model, and a single overall computation is distributed across multiple processes or devices.

(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;

(i) Yes, PHP is a case sensitive language both upper and lower case are treated differently.
(ii) Example: $x and $X are different variable names.

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

Google chrome, Firefox, Safari, Opera, Internet Explorer, Netscape Navigator etc.

Web scripting languages are classified into two types.
(i) Client side scripting language
(ii) Server side scripting language.

(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.