Server side scripting language

Server Side Scripting Language
10/29/2019By Girmachew Gulint (Mtech CSE) 1
A typical web server today contains four elements
in addition to the physical hardware.
LAMP (Linux, Apache, MySQL, and PHP)
WAMP (Windows, Apache, MySQL, & PHP)
XAMPP (Apache, MariaDB , Perl and PHP)
 PHP
 ASP
 Perl

PHP( Personal Home Page/Hypertext Preprocessor )
• Created in 1994 at the hands of Rasmus Lerdorf.
• a server-side language, which means it runs on the server before anything is sent to
the user’s computer.
Some advantages of server-side language
• Code is hidden from the user
• Secure what is take place in the background
• Reduce users computer load even through it needs powerful server.

WHY PHP
• PHP runs on numerous, varying platforms, including Windows, Linux, Unix, Mac
OS X, and so on.
• PHP is compatible with almost any modern server, such as Apache, IIS, and more.
• PHP supports a wide range of databases.
• PHP is free!
• PHP is easy to learn and runs efficiently on the server side.
• PHP is faster than other scripting language e.g. asp and jsp.

Syntax
Tag style Starting tag Ending tag
Standard <?php ?>
Short hand <? ?>
ASP <% %>
Script <script language=“php> </script>
php can be saved .php or embeded into html.

Example
• <?php
• echo “Hello world”;
• ?>
• <?
• ?>
• <%
• %>

PHP-Errors
1. Notice: noticing the programmer.
2. Warning : something has gone wrong during the execution of a script.
3. Error : unrecoverable(execution will stop); typically parsing error like
missing semicolon, function or other problem the engine does not know
how to resolve. Another category of error is logical error.

Send output to the browser
With PHP, there are two basic ways to get output: echo and print.
1. echo;
2. print();
• The differences : echo has no return value while print has a return value of
1 so it can be used in expressions.
• echo can take multiple parameters (although such usage is rare) while print
can take one argument. echo is marginally faster than print.

Comment
1. // single line comment
2. # this is also single line comment
3. /* multi line comment */

Variables
• Are special container of user defined values. Values can be number, string or
Boolean or other.
• Variables use to create template for operation.
• Variable consist name of your choosing preceded by $. (meaningful)
• Variable name can include letter, number and underscore but not include
space
• Variable must start by underscore or letter only

Example
Good variable Bad variable
$name $1name
$age $+age
$firstName $first name
$_salary $1a2a3a

Availability of variables
1. Local : their life time is inside function only.
2. global/ superglobal : accessible globally or superglobally.

Data types
• Different types of data take up different amounts of memory and may be
treated differently when they are manipulated in a script.
• Some programming languages therefore demand that the programmer
declare in advance which type of data a variable will contain. By contrast,
PHP is loosely typed, meaning that it will calculate data types as data is
assigned to each variable.

Continued
PHP supports 8 primitive data types that can be categorized further in 3 types:
• Scalar Types
• Compound Types
• Special Types

Data types
Scala data types Compound data types Special data types
Boolean Array Resource
Integer Object Null
Float
Double
String

gettype() and settype() or casting
• $name = “Girmachew “;
• gettype($name);// will output String
• //casting data type
• $number = 4.5;
• echo gettype($number);
• settype($number, 'string'); // converting into string
• echo gettype($number);

Constant
PHP constants are name or identifier that can't be changed during the
execution of the script. PHP constants can be defined by 2 ways:
• Using define() function
• Using const keyword
• PHP constants follow the same PHP variable rules. For example, it can be
started with letter or underscore only.
• Conventionally, PHP constants should be defined in uppercase letters.

PHP constant: define()
• Let's see the syntax of define() function in PHP.
define(name, value, case-insensitive)
Example
• <?php
• define("MESSAGE","Hello JavaTpoint PHP");
• echo MESSAGE;
• ?>

PHP constant: const keyword
• The const keyword defines constants at compile time. It is a language construct not a function.
• It is bit faster than define().
• It is always case sensitive.
• Example
• <?php
• const MESSAGE="Hello const by JavaTpoint PHP";
• echo MESSAGE;
• ?>

Server side scripting language

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