Introduction to PHP and Conditional Statements

WHAT IS HTML?
HTML is a markup language for describing web
documents (web pages).
• HTML stands for Hyper Text Markup Language
• A markup language is a set of markup tags
• HTML documents are described by HTML tags
• Each HTML tag describes different document content

What is PHP?
• PHP is an acronym for "PHP: Hypertext
Preprocessor“.
• PHP is a widely-used, open source scripting
language.
• PHP scripts are executed on the server and the
plain HTML result is sent back to the browser.
• PHP is free to download and use.

What is a PHP File?
• PHP files can contain text, HTML, CSS, JavaScript,
and PHP code.
• PHP code are executed on the server, and the
result is returned to the browser as plain HTML.
• PHP files have extension ".php“.

What Can PHP Do?
• PHP can generate dynamic page content
• PHP can create, open, read, write, delete, and close files on the server
• PHP can collect form data
• PHP can send and receive cookies
• PHP can add, delete, modify data in your database
• PHP can be used to control user-access
• PHP can encrypt data
• With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash
movies. You can also output any text, such as XHTML and XML.

Why PHP?
• PHP runs on various platforms (Windows, Linux, Unix,
Mac OS X, etc.)
• PHP is compatible with almost all servers used today
(Apache, IIS, etc.)
• PHP supports a wide range of databases
• PHP is free. Download it from the official PHP resource:
www.php.net
• PHP is easy to learn and runs efficiently on the server side

What Do I Need?
To start using PHP, you can:
• Find a web host with PHP and MySQL support
• Install a web server on your own PC, and then
install PHP and MySQL

Use a Web Host With PHP Support
If your server has activated support for PHP you
do not need to do anything. Just create some .php
files, place them in your web directory, and the
server will automatically parse them for you. You
do not need to compile anything or install any
extra tools. Because PHP is free, most web hosts
offer PHP support.

Set Up PHP on Your Own PC
However, if your server does not support PHP, you
must:
• install a web server.
• install PHP.
• install a database, such as MySQL.
The official PHP website (PHP.net) has installation
instructions for PHP:
http://php.net/manual/en/install.php

Basic PHP Syntax
• A PHP script can be placed anywhere in the
document.
• A PHP script starts with <?php and ends with ?>.
• The default file extension for PHP files is ".php".
• A PHP file normally contains HTML tags, and some
PHP scripting code.

Comments in PHP
A comment in PHP code is a line that is not
read/executed as part of the program.
Comments can be used to:
• Let others understand what you are doing
• Remind yourself of what you did - Most programmers have
experienced coming back to their own work a year or two
later and having to re-figure out what they did. Comments
can remind you of what you were thinking when you wrote
the code.

EXAMPLE
<?php
// This is a single-line comment
# This is also a single-line comment
/*
This is a multiple-lines comment block
that spans over multiple
lines
*/
// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
echo $x;
?>

PHP Case Sensitivity
In PHP, all keywords (e.g. if, else, while, echo, etc.),
classes, functions, and user-defined functions are
NOT case-sensitive.
However; all variable names are case-sensitive.

VARIABLES: Variables are "containers"
for storing information.
Creating (Declaring) PHP Variables:
In PHP, a variable starts with the $ sign, followed by
the name of the variable:
Example:<?php
$x=10.5;
$y=4;
$var1=“Hello World”;
$var2=‘ Hello World’;

Rules for PHP Variable
• A variable starts with the $ sign, followed by the name of the variable
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and
underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive ($age and $AGE are two different
variables)
NOTE: PHP variables are case-sensitive.

Output Variables
The PHP echo statement is often used to output data to the
screen.
EXAMPLE 1: <?php
$var = “WORLD";
echo “HELLO $var!";
?>
EXAMPLE 2: <?php
$var = “world";
echo "I love " . $var . "!";
?>

PHP is a Loosely
Typed Language

In previous examples, notice that we did not have
to tell PHP which data type the variable is. PHP
automatically converts the variable to the correct
data type, depending on its value. In other
languages such as C, C++, and Java, the
programmer must declare the name and type of
the variable before using it.

In PHP, variables can be declared anywhere in the
script.
The scope of a variable is the part of the script where
the variable can be referenced/used.PHP has three
different variable scopes:
• local
• global
• static

GLOBAL SCOPE
A variable declared outside a function has a GLOBAL
SCOPE and can only be accessed outside a function.
The global keyword is used to access a global variable
from within a function.
EXAMPLE: <?php
$var=“HELLO WORLD!”;
/*function declaration*/
function hello()
{
Global $var;
echo $var;
}
hello();
?>

LOCAL SCOPE
A variable declared within a function has a LOCAL SCOPE
and can only be accessed within that function.
EXAMPLE: <?php
function hello()
{
//local variable declaration
$var=“HELLO WORLD”;
echo $var;
}
hello();
?>

STATIC SCOPE
Normally, when a function is Completed/executed, all of its variables
are deleted. However, sometimes we want a local variable NOT to be
deleted. We need it for a further job. To do this, use
the static keyword when you first declare the variable.
EXAMPLE: <?php
function myTest()
{
static $x = 0;
echo $x;
$x++;
}
myTest();
myTest();
?>
Then, each time the function is called, that variable will still have the
information it contained from the last time the function was called.

echo and print are more or less the same. They are
both used to output data to the screen.
The differences are small: 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.

The PHP echo Statement
The echo statement can be used with or without
parentheses: echo or echo().
EXAMPLE: <?php
echo “<h1>HELLO WORLD</h2>”;
echo "PHP is Fun!</br>";
echo "This ", "string ", "was ",
"made ", "with multiple parameters.“;
?>
NOTE: That the text can contain HTML markup.

The PHP print Statement
The print statement can be used with or without
parentheses: print or print().
It can’t take parameters and HTML tags.

PHP supports the following
data types:
• String
• Integer
• Float (floating point numbers - also called double)
• Boolean
• Array
• Object
• NULL
• Resource

PHP String
A string is a sequence of characters. A string can be
any text inside quotes. You can use single or double
quotes.
EXAMPLE:
<?php
$var=“HELLO”;
echo ”This is String $var ”;
echo ‘This is a string’ . $var;
?>

PHP Integer
An integer data type is a non-decimal number
Between -2,147,483,648 and 2,147,483,647.
Rules for integers:
• An integer must have at least one digit.
• An integer must not have a decimal point.
• An integer can be either positive or negative.
• Integers can be specified in three formats: decimal (10-
based), hexadecimal (16-based - prefixed with 0x) or octal
(8-based - prefixed with 0).
EXAMPLE: <?php
$x = 5985;
var_dump($x);
?>
NOTE: The PHP var_dump() function returns the data
type and value.

PHP Float
A float (floating point number is also called double) is
a number with a decimal point or a number in
exponential form.
EXAMPLE:
<?php
$x = 10.365;
var_dump($x);
?>

PHP Boolean
A Boolean represents two possible states: TRUE
or FALSE. Booleans are often used in conditional
testing.
EXAMPLE:
$x = true;
$y = false;

PHP Array
An array stores multiple values in one single
variable.
Example:
<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>

PHP Objects
An object is a data type which stores data and information on how
to process that data. In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class
keyword. A class is a structure that can contain properties and
methods.
EXAMPLE: <?php
class Ex1 {
function Ex2()
{
$this->Var= “HELLO WORLD";
}
}
// create an object
$obj= new Ex1();
// show object properties
echo $obj->Var;
?>

NULL Value
Null is a special data type which can have only one
value: NULL. A variable of data type NULL is a variable
that has no value assigned to it.
NOTE: If a variable is created without a value, it is
automatically assigned a value of NULL.
Example: <?php
$x = null;
var_dump($x);
?>

Resourse
• The special resource type is not an actual data
type. It is the storing of a reference to functions
and resources external to PHP.
• A common example of using the resource data
type is a database call.

Strlen
The PHP strlen() function returns the length of a
string.
EXAMPLE: <?php
echo strlen("Hello world!");
?>

Str_word_count
The PHP str_word_count() function counts the
number of words in a string.
EXAMPLE: <?php
echo str_word_count("Hello world!");
?>

Strrev
The PHP strrev() function reverses a string.
EXAMPLE: <?php
echo strrev("Hello world!");
?>

• A constant is an identifier (name) for a simple value.
The value cannot be changed during the script.
• A valid constant name starts with a letter or
underscore (no $ sign before the constant name).
• To create a constant, use the define() function.
Note: Unlike variables, constants are automatically
global across the entire script.

SYNTAX
define(name, value, case-insensitive)
Parameters:
• name: Specifies the name of the constant
• value: Specifies the value of the constant
• case-insensitive: Specifies whether the constant name
should be case-insensitive. Default is false

Constant are Global
Constants are automatically global and can be
used across the entire script.

Operators are used to perform operations on
variables and values.
PHP divides the operators in the following groups:
• Arithmetic operators
• Assignment operators
• Comparison operators
• Increment/Decrement operators
• Logical operators
• String operators
• Array operators

PHP Arithmetic Operators
The PHP arithmetic operators are used with numeric
values to perform common arithmetical operations,
such as addition, subtraction, multiplication etc.
OPERATOR NAME
EXAMPL
E
RESULT
+ Addition
$x + $y Sum of x and y
- Subtraction
$x - $y Difference of x
and y
* Multiplication
$x * $y Product of x
and y
/ Divide
$x / $y Quotient of $x
and $y
% Modulus
$x % $y Remainder of
x and y

PHP Assignment Operators
The PHP assignment operators are used with numeric
values to
write a value to a variable. The basic assignment
operator in PHP
is "=". It means that the left operand gets set to the
value
of the assignment expression on the right.
Assignment Same as Description
x = y x = y The left operand gets set to
the value of the expression
on the right
x += y x = x + y Addition
x -= y x = x - y Subtraction

Comparison Operators
The PHP comparison operators are used to
compare two values (number or string).
Operator Name Example Result
== Equal $x == $y Returns true if
$x is equal to $y
=== Identical $x === $y Returns true if
$x is equal to $y,
and they are of
the same type
!= Not equal $x != $y Returns true if
$x is not equal to
$y
<> Not equal $x <> $y Returns true if
$x is not equal to
$y

!== Not identical $x !== $y Returns true if $x is not
equal to $y, or they are
not of the same type
> Greater than $x > $y Returns true if $x is
greater than $y
< Less than $x < $y Returns true if $x is less
than $y
>= Greater than
or equal to
$x >= $y Returns true if $x is
greater than or equal to
$y
<= Less than or
equal to
$x <= $y Returns true if $x is less
than or equal to $y

PHP Increment / Decrement Operators
• The PHP increment operators are used to increment a
variable's value.
• The PHP decrement operators are used to decrement a
variable's value.
Operator Name Description
++$x Pre-increment Increments $x by one,
then returns $x
$x++ Post-increment Returns $x, then
increments $x by one
--$x Pre-decrement Decrements $x by one,
then returns $x
$x-- Post-decrement Returns $x, then

PHP Logical Operators
The PHP logical operators are used to combine
conditional statements.
and And $x and $y True if both $x and
$y are true
or Or $x or $y True if either $x or
$y is true
xor Xor $x xor $y True if either $x or
$y is true, but not
both
&& And $x && $y True if both $x and
$y are true
|| Or $x || $y True if either $x or
$y is true
! Not !$x True if $x is not

PHP String Operators
PHP has two operators that are specially
designed for strings.
. Concatenat
ion
$txt1 .
$txt2
Concatenat
ion of $txt1
and $txt2
.= Concatenat
ion
assignmen
t
$txt1 .=
$txt2
Appends
$txt2 to
$txt1

PHP Array Operators
The PHP array operators are used to compare
arrays.
+ Union $x + $y Union of $x and $y
== Equality $x == $y Returns true if $x
and $y have the
same key/value
pairs
=== Identity $x === $y Returns true if $x
and $y have the
same key/value
pairs in the same
order and of the
same types

!= Inequality $x != $y Returns true if
$x is not equal
to $y
<> Inequality $x <> $y Returns true if
$x is not equal
to $y
!== Non-identity $x !== $y Returns true if
$x is not
identical to $y

Very often when you write code, you want to perform
different actions for different conditions. You can use
conditional statements in your code to do this.
In PHP we have the following conditional statements:
• if statement - executes some code if one condition is
true
• if...else statement - executes some code if a condition
is true and another code if that condition is false
• if...elseif....else statement - executes different codes
for more than two conditions
• switch statement - selects one of many blocks of
code to be executed

The if Statement
The if statement executes some code if one
condition is true.
Syntax:
if (condition)
{
code to be executed if condition is true;
}

The if...else Statement
The if....else statement executes some code if a
condition is true and another code if that
condition is false.
Syntax 1: if (condition)
{
}
Else
{
code to be executed if condition is false;
}

Syntax 2:
if (condition) :
else:
code to be executed if condition is false;
end if;
Note: In the place of curly braces ({}) we can also
use semi colon (:).

The if...elseif....else Statement
The if....elseif...else statement executes different
codes for more than two conditions.
Syntax: if (condition) :
code to be executed if this condition is true; elseif
(condition) :
code to be executed if this condition is true;
else :
code to be executed if all conditions are false;
end if else;

The switch Statement
Use the switch statement to select one of many
blocks of code to be executed.
Syntax: switch (n) {
case label1:
code to be executed if n=label1;
break;
case label2:
break;
case label3:
break;
...
default:
code to be executed if n is different from all labels;
}

Often when you write code, you want the same
block of code to run over and over again in a row.
Instead of adding several almost equal code-lines in
a script, we can use loops to perform a task like this.
In PHP, we have the following looping statements:
• while - loops through a block of code as long as the
specified condition is true
• do...while - loops through a block of code once, and
then repeats the loop as long as the specified
condition is true
• for - loops through a block of code a specified
number of times
• foreach - loops through a block of code for each
element in an array

The PHP while Loop
The while loop executes a block of code as long
as the specified condition is true.
Syntax:
while (condition is true):
code to be executed;
end while;

The PHP do...while Loop
The do...while loop will always execute the block
of code once, it will then check the condition,
and repeat the loop while the specified condition
is true.
Syntax:
do
{
}
while (condition is true);

The PHP for Loop
The for loop is used when you know in advance
how many times the script should run.
Syntax:
for (init counter; test counter; increment counter)
{
}
Parameters:
• init counter: Initialize the loop counter value.
• test counter: Evaluated for each loop iteration. If it
evaluates to TRUE, the loop continues. If it evaluates to
FALSE, the loop ends.
• increment counter: Increases the loop counter value.

The PHP foreach Loop
The foreach loop works only on arrays, and is
used to loop through each key/value pair in an
array.
Syntax:
foreach ($array as $value)
{
}

• Besides the built-in PHP functions, we can create
our own functions.
• A function is a block of statements that can be
used repeatedly in a program.
• A function will not execute immediately when a
page loads.
• A function will be executed by a call to the
function.

Create a User Defined Function
in PHP
A user defined function declaration starts with
the word "function“.
Syntax:
function functionName()
{
}

Note:
1)A function name can start with a letter or
underscore (not a number).
2)Give the function a name that reflects what the
function does.
2)Function names are NOT case-sensitive.

PHP Function Arguments
Information can be passed to functions through
arguments. An argument is just like a variable.
Arguments are specified after the function name,
inside the parentheses. You can add as many
arguments as you want, just separate them with a
comma.
Syntax: function functionName(arg1,arg2,arg3……)
{
}

PHP Default Argument Value
If we call the function without arguments it takes
the default value as argument.
EXAMPLE:
<?php
function setHeight($minheight = 50)
{
echo "The height is : $minheight <br>";
}
setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
?>

Introduction to PHP and Conditional Statements

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Introduction to PHP and Conditional Statements