Php, Lecture notes of Computer Engineering and Programming

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1

LAMPP Installation

on Ubuntu

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LAMPP Installation on Ubuntu

http://howtoubuntu.org/how-to-install-lamp-on-

ubuntu

https://www.digitalocean.com/community/tutoria

ls/how-to-install-linux-apache-mysql-php-lamp-

stack-on-ubuntu

Sublime Editor for LINUX platform

http://monkeyhacks.com/post/how-to-install-

sublime-text-2-on-ubuntu-14-

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4

Escaping to PHP

• The PHP parsing engine needs a way to differentiate

PHP code from other elements in the page.

• The mechanism for doing so is known as ‘ escaping to

PHP ’.

• All PHP statements end with a semi-colon
• Each PHP script must be enclosed in the reserved PHP

tag

<?php

// PHP code goes here …

?>

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5

A PHP script can be placed

anywhere in the document

A PHP script starts with

The default file extension

for PHP files is “.php”

A PHP file normally

contains HTML tags , and

some PHP scripting code

PHP Syntax Overview

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Commenting PHP Code

• Multi-lines comments: They are generally used to provide

pseudocode algorithms and more detailed explanations when

necessary. The multiline style of commenting is the same as in C

<? / This is a multiline comment*

Author : Shivani Nanda

Purpose: Multiline Comments Demo

Subject: PHP

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8

PHP is Whitespace insensitive

• PHP whitespace insensitive means that it almost never matters

how many whitespace characters you have in a row i.e. one

whitespace character is the same as many such characters

<?

$four = 2 + 2; // single spaces

$four =<tab2+2 ; // spaces and tabs

$four =

2+

2; // multiple lines

?>

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10

PHP : Case Sensitive for Variables

PHP variables must begin with a “$” sign

Case-sensitive ($Foo != $foo != $fOo)

Certain variable names reserved by PHP

Form variables ($_POST, $_GET)

Server variables ($_SERVER)

Etc.

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$greeting = "Welcome to PHP!";

Statements are expressions terminated by ;

• A statement in PHP is any expression that is followed by a semicolon (;)
• Any sequence of valid PHP statements that is enclosed by the PHP tags is

a valid PHP program

• The above line represents a typical statement in PHP, which in this case

assigns a string of characters to a variable called $greeting

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13

Braces make Blocks

• Although statements cannot be combined like

expressions, we can always put a sequence

of statements anywhere a statement can go by enclosing

them in a set of curly braces

Here both statements are equivalent

if (3 = = 2 + 1)

print(“Good - I haven‘t totally lost my mind ”);

if (3 = = 2 + 1)

{ print(“Good - I haven’t totally”);

print(“lost my mind.
”); }

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14

PHP : Variable Types

• All variables in PHP are denoted with a leading

dollar sign ($)

• The value of a variable is the value of its most

recent assignment

• Variables are assigned with the = operator, with the

variable on the left-hand side and the expression to

be evaluated on the right

• Variables can, but do not need, to be declared before

assignment

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PHP : Data Types for Variables

• PHP has a total of eight data types which we use to construct

our variables:

• Integers: are whole numbers, without a decimal point, like

4195

• Doubles: are floating-point numbers, like 3.14159 or 49.
• Booleans: have only two possible values either true or false
• NULL: is a special type that only has one value: NULL

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PHP : Data Types for Variables

• Strings: are sequences of characters, like 'PHP supports

string operations.’

• Arrays: are named and indexed collections of other

values

• Objects: are instances of programmer-defined classes,

which can package up both other kinds of values and

functions that are specific to the class

• Resources: are special variables that hold references to

resources external to PHP (such as database connections)

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They are whole numbers, without a decimal

point,

like 4195

They are the simplest type

They correspond to simple whole numbers, both

positive and negative

Integer

$int_var = 12345;

// Integers can be assigned to variables

$another_int = -12345 + 12345;

// or used in expressions

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20

Boolean

• They have only two possible values either true or false
• PHP provides a couple of constants especially for use as

Booleans: TRUE and FALSE

if (TRUE)

print(“This will always print
”);

else

print(“This will never print
”);