Three types of PHP Syntax are available.
They are as follows
1. Default Syntax
2. Short open tags
3. HTML Script embed Tags

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;

(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) Resource is a specific variable.
(ii) It hasa reference to an external resource .
(iii) These variables hold specific handlers to handle files and database connections irrespective PHP program.

(i) The var_dump( ) function is used to dump information about a variable.
(ii) This function displays structured information such as type and value of the given variable.
(iii) Arrays and objects are explored recursively with values indented to show structure.
Example:
\($\)x = "COMPUTER APPUCATION!";
\($\)x = null;
var dump(\($\)x);
?>
OUTPUT: NULL

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.

Default Syntax:
The default Syntax begins with " < ?php"and closes with "? > ".

Short open Tags
(i) The Short open Tags begins with " < ?" andcloses with "? > " .
(ii) But admin user has to enable Short style tags settings in php.ini file on the server.

HTML Script embed Tags:
HTML Script embed Tags looks just like HTML scripts tags.

PHP scripting language supports 13 primitive data types.
PHP supports the following data types.
(i) String
(ii) Integer
(iii) Float
(iv) Boolean
(v) Array
(vi) Object
(vii) NULL
(viii) Resource
(i) String
String is a collection of characters within the double quotes ("") or single quotes ().
Space is also considered as a character.
Example:
$x= "Computer Application";
$y='Computer Application';
(ii) Integer
Data type which contains non decimal numbers.
Example (i) $x=59135;
Example (ii)
$x = 59135;
var_dump($x);
The var_dump() function returns type and value about variables in PHP.
(iii) Float
Float is a data type which contains decimal numbers.
Example Sx=19.15;
$x = 19.15;
var_dump($x);
?>
(iv) Boolean
Boolean is a data type which returns two possible states, TRUE or FALSE.
Example:
$x = true;
$y = false;
echo $x;
echo $y;
(v) Array
Array is a data type which has multiple values in single variable.
Example:
$cars
= array("Computer", "Laptop", "Mobile");
var_dump(Scars);
?>
Output:
array(3) {[0]=> string(5) "Computer" [1]=>
string(3) "Laptop" [2]=> string(6) "Mobile"}
(vi) Object
Object is a data type which contains information about data and function inside the class.
Example:
class School {
function marks() {
$this->sec =
       }
}
// create an object
$school_obj= new School ();
// show object properties
echo Sschool_obj ->sec;
?>
(vii) NULL
It is a special data type which contains a single value: NULL.
Example:
$x="COMPUTER APPLICATION!";
$x = null;
var_dump($x);
?>
Output: NULL
(viii) Resources
It is a specific variable, it has a reference to an external resource.
These variables hold specific handlers to handle files and database connections.
// Open a file for reading
$handle = fopen("note.txt", "r");
var_dump($handle);
echo "
";
// Connect to MySQL database server with default setting
$link= mysql_connect("localhost", "root", "");
var_dump($link);
?>

Website development has done by the following activities.
1. Website or webpage is developed by the programmer using PHP script.
2. Entire website codes are moved to web server path in a remote server machine.
3. From the client side, the end user open a browser, types the URL of the website (or) webpage and initiates the request to remote server machine over the network.
4. After receiving the request from client machine the web server tries to compile and interpret the PHP code which is available in remote machine.
5. Response will be generated and sent back to the client machine over the network from webserver.
6. Finally the browser is installed in the client machine receives the response and displays the output to user, as shown in fig.

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.