INTRODUCTION ON PHP - SERVER SIDE SCRIPTING LANGUAGE

Introduction
• PHP is an acronym for "PHP: Hypertext Preprocessor"
• PHP is a widely-used, open source scripting language
• PHP scripts are executed on the server
• PHP is free to download and use
• PHP files can contain text, HTML, CSS, JavaScript, and
PHP code
• PHP code is executed on the server, and the result is
returned to the browser as plain HTML
• PHP files have extension ".php"

Introduction(Contd.,)
• 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 or PDF files. You can also output
any text, such as XHTML and XML.

Why?
• 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’s New in PHP?
• PHP 7 is much faster than the previous
popular stable release (PHP 5.6)
• PHP 7 has improved Error Handling
• PHP 7 supports stricter Type Declarations for
function arguments
• PHP 7 supports new operators (like the
spaceship operator: <=>)

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 is executed on the server, and the
plain HTML result is sent back to the browser.
• <?php
// PHP code goes here
?>
• The default file extension for PHP files is
".php".
• A PHP file normally contains HTML tags, and
some PHP scripting code.

Sample PHP file
• <!DOCTYPE html>
<html>
<body>
<h1>My first PHP page</h1>
<?php
echo "Hello World!";
?>
</body>
</html>

PHP Case Sensitivity
• In PHP, keywords (e.g. if, else, while, echo, etc.), classes, functions,
and user-defined functions are not case-sensitive.
• In the example below, all three echo statements below are equal
and legal:
• <!DOCTYPE html>
<html>
<body>
<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>
</body>
</html>

• Look at the example below; only the first statement
will display the value of the $color variable! This is
because $color, $COLOR, and $coLOR are treated as
three different variables:
• <!DOCTYPE html>
<html>
<body>
<?php
$color = "red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>
</body>
</html>

Comments in PHP
• <!DOCTYPE html>
<html>
<body>
<?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
*/
?>
</body>
</html>

Creating (Declaring) PHP Variables
• In PHP, a variable starts with the $ sign,
followed by the name of the variable:
• <?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>

PHP Variables
Rules for PHP variables:
• 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)

Example
• <?php
$txt = “Universe";
echo "I love $txt!";
?>
• <?php
$txt = “Universe";
echo "I love " . $txt . "!";
?>

PHP is a Loosely Typed Language
• In the example above, notice that we did not
have to tell PHP which data type the variable is.
• PHP automatically associates a data type to the
variable, depending on its value. Since the data
types are not set in a strict sense, you can do
things like adding a string to an integer without
causing an error.
• In PHP 7, type declarations were added. This
gives an option to specify the data type expected
when declaring a function, and by enabling the
strict requirement, it will throw a "Fatal Error" on
a type mismatch.

PHP Variables Scope
• 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 and Local Scope
• A variable declared outside a function has a
GLOBAL SCOPE and can only be accessed outside
a function:
• <?php
$x = 5; // global scope
function myTest() {
// using x inside this function will generate an
error
echo "<p>Variable x inside function is: $x</p>";
}
myTest();
echo "<p>Variable x outside function is: $x</p>";
?>
Output:
Variable x inside function is:
Variable x outside function is: 5

Variable with local scope:
• <?php
function myTest() {
$x = 5; // local scope
echo "<p>Variable x inside function is: $x</p>";
}
myTest();
// using x outside the function will generate an
error
echo "<p>Variable x outside function is: $x</p>";
?>
Output:
Variable x inside function is: 5
Variable x outside function is:

PHP echo and print Statements
• 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.

Examples
<!DOCTYPE html>
<html>
<body>
<?php
echo "<h2>PHP is Fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This ", "string ", "was ", "made ", "with multiple parameters.";
?>
</body>
</html>
Output:
PHP is Fun!
Hello world!
I'm about to learn PHP!
This string was made with multiple
parameters.

Examples
<?php
$txt1 = "Learn PHP";
$txt2 = “Its easy to learn";
$x = 5;
$y = 4;
echo "<h2>" . $txt1 . "</h2>";
echo "Study PHP at " . $txt2 . "<br>";
echo $x + $y;
?>
Output:
Study PHP at Its easy to learn
9

Display Variables
<?php
$txt1 = "Learn PHP";
$txt2 = “All";
$x = 5;
$y = 4;
print "<h2>" . $txt1 . "</h2>";
print "Study PHP at " . $txt2 . "<br>";
print $x + $y;
?>
Output:
Study PHP at All
9

PHP Data Types
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, like "Hello
world!".
• A string can be any text inside quotes. You can
use single or double quotes:
<?php
$x = "Hello world!";
$y = 'Hello world!';
echo $x;
echo "<br>";
echo $y;
?>

PHP Integer
• 2, 256, -256, 10358, -179567 are all integers.
• An integer is a number without any decimal part.
• An integer data type is a non-decimal number
between -2147483648 and 2147483647 in 32 bit
systems, and between -9223372036854775808
and 9223372036854775807 in 64 bit systems.
• A value greater (or lower) than this, will be stored
as float, because it exceeds the limit of an integer.
• Note: Another important thing to know is that
even if 4 * 2.5 is 10, the result is stored as float,
because one of the operands is a float (2.5).

• Here are some 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)

• PHP has the following predefined constants
for integers:
• PHP_INT_MAX - The largest integer supported
• PHP_INT_MIN - The smallest integer
supported
• PHP_INT_SIZE - The size of an integer in bytes

• PHP has the following functions to check if the
type of a variable is integer:
• is_int()
• is_integer() - alias of is_int()
• is_long() - alias of is_int()

Example
<!DOCTYPE html>
<html>
<body>
<?php
// Check if the type of a variable is integer
$x = 5985;
var_dump(is_int($x));
echo "<br>";
// Check again...
$x = 59.85;
var_dump(is_int($x));
?>
</body>
</html>
Output:
bool(true)
bool(false)

INTRODUCTION ON PHP - SERVER SIDE SCRIPTING LANGUAGE

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