Introduction to php basics

PHP
PHP Hypertext Pre-processor
‚PHP is a server side scripting language‛
“Personal home page”

Generate HTML
Get index.php
1
3
4
pass index.php to PHP
interpretor
5
WebServer
Index.php in interpreted
HTMl form
Browser
2
Get index.php from
hard disk
What you mean by hypertext Pre-processor?

Scripting Languages
• A ‚script‛ is a collection of program or sequence of instructions that is
interpreted or carried out by another program rather than by the computer
processor. Two types of scripting languages are
– Client-side Scripting Language
– Server-side Scripting Language
• In server-side scripting, (such as PHP, ASP) the script is processed by the
server Like: Apache, ColdFusion, ISAPI and Microsoft's IIS on Windows.
• Client-side scripting such as JavaScript runs on the web browser.

What you mean by server side scripting??
•
Generate HTML
Get index.php
1
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interpretor
5
WebServer
HTMl form
Browser
2
Get index.php from
hard disk
PHP is server side scripting
language because the php code
runs on the server and returns
the result in html form to the
client browser

What you mean by client side scripting??
•
Generate HTML
Get index.php
1
3
4
interpretor
5
WebServer
HTMl form
Browser
2
Get index.php from
hard disk
Client side scripting is something
where code runs on client
side(browser). For eg checking
whether a HTML text field contains
data or not can be done by running
a script from browser itself

How to create a PHP page
1. Install Wamp (Windows-Apache-Mysql-PHP)
2. Create a new folder within WampWWW folder with the name
you want to give your project
• Eg: C:WampWWWmyProject
3. Right click and Create a new text file with extention ‚.php‛
• Eg: index.php

How to run PHP program
1. Start Wamp Server
2. Open your browser and type localhost/myProject/
3. Most of the browsers load the file with name ‚index‛ automatically. So it
is recommended to have the name ‚index‛ for your home page

Getting started with PHP programming

PHP Syntax
 Structurally similar to C/C++
 Supports procedural and object-oriented paradigm (to some degree)
 All PHP statements end with a semi-colon
 Each PHP script must be enclosed in the reserved PHP tag
<?php
//PHP code goes here..
?>

Other PHP tags
<?php
... Code
?>
Standard Tags
<?
... Code
?>
<?= $variable ?>
<script language=“php”>
... Code
</script>
<%
... Code
%>
Short Tags
Script TagsASP Tags

Commenting
// comment single line
/* comment
multiple lines */
//comment single line
/* Comment
multiple Lines*/
# comment single line-shell style
C PHP

Data types
• PHP supports many different data types, but they are generally
divided in two categories:
• Scalar
» boolean :A value that can only either be true or false
» Int :A signed numeric integer value
» float : A signed floating-point value
» string : A collection of binary data
• Composite.
» Arrays
» Objects

Type Casting
 echo ((0.1 + 0.7) * 10); //Outputs 8
 echo (int) ((0.1 + 0.7) * 10); //Outputs 7
• This happens because the result of this simple arithmetic
expression is stored internally as 7.999999 instead of 8; when the
value is converted to int, PHP simply truncates away the fractional
part, resulting in a rather significant error (12.5%, to be exact).

Declaring a variable
//Declaring a variable
Int a=10;
Char c=‘a’;
Float f=1.12;
//Every variable starts with ‚$‚sign
//No need of prior Declarations
$a=10;
$c=‘a’;
$f=1.12;
C PHP

Variables
• Variables are temporary storage containers.
• In PHP, a variable can contain any type of data, such as, for example,
strings, integers, floating numbers, objects and arrays.
• PHP is loosely typed, meaning that it will implicitly change the type of a
variable as needed, depending on the operation being performed on its
value.
• This contrasts with strongly typed languages, like C and Java, where
variables can only contain one type of data throughout their existence.

Variable Variables
• In PHP, it is also possible to create so-called variable variables.
That is a variable whose name is contained in another variable.
For eg:
$name = ’foo’;
$$name = ’bar’;
echo $foo; // Displays ’bar’
function myFunc()
{
echo ’myFunc!’;
}
$f = ’myFunc’;
$f(); // will call myFunc();

Determining If a Variable Exists
• There is an inbuilt method called isset() which will return true if a
variable exists and has a value other than null
$x=12;
echo isset ($x); // returns true
echo isset($y); // returns false

Declaring a constant
//Declaring a constant using ‘const’
const int a=10;
int const a=10;
//Declaring a constant using ‘#define’
#define TRUE 1
#define FALSE 0
#define NAME_SIZE 20
define(’name’, ’baabtra’);
define(’EMAIL’, ’davey@php.net’);
echo EMAIL; // Displays ’davey@php.net’
echo name.PHP_EOL.email;
// Displays ’baabtra;
‘davey@php.net’
C PHP

Constants
• Conversely to variables, constants are meant for defining immutable values.
• Constants can be accessed for any scope within a script; however, they can
only contain scalar values.
• The built-in PHP_EOL constant represents the ‚end of line‛ marker.

output
Int a=10,b=25;
Printf(‚%d %d‛,a,b);
$a=10; $b=25
Printf(‚%d %d‛,$a,$b);
print $a;
print $b; //Cannot take multiple arguments
echo $a,$b; //Fast and commonly used
die(‚the end‛);
exit(‚the end‛); // both allows to terminate
the script’s output by outputting a string
C PHP

echo Vs print
• echo is a language construct ( Constructs
are elements that are built-into the language
and, therefore, follow special rules)
• echo doesnt have a return value
• print() is not a language construct. It
is an inbuilt function only
• Always return 1 once it print
someting

Control Structures
Conditional Control Structures
• If
• If else
• Switch
Loops
For
While
Do while
Other
• Break
• Continue
‚Exactly the same as on left side‛
C PHP

Functions
Int findSum(int a,int b)
{
Int c;
c=a+b;
Return c
}
findSum(10,15);
function findSum($a,$b)
{
$c=$a+$b;
Return $c;
}
findSum(10,15);
C PHP

Function arguments
• You can define any number of arguments and, in fact, you can pass an
arbitrary number of arguments to a function, regardless of how many you
specified in its declaration.PHP will not complain unless you provide fewer
arguments than you declared
Eg:
function greeting($arg1)
{
echo ‚hello $ arg1‛;
}
greeting(‚baabtra‛);
greeting(‚baabtra‛, ‛baabte‛);
greeting(); // ERROR

Function arguments
• You can make arguments optional by giving them a default value.
function hello($who = "World")
{
echo "Hello $who";
}
hello(‘baabtra’); // hello baabtra
hello(); // hello world

Function arguments
PHP provides three built-in functions to handle variable-length
argument lists:
– func_num_args() : return the total number of arguments
– func_get_arg() : return the argument at any index position
– func_get_args() : returns an array of all argument

Function arguments
function hello()
{
if (func_num_args() > 0)
{
$arg = func_get_arg(0); // The first argument is at position 0
echo "Hello $arg";
}
else
{
echo "Hello World";
}
}
hello("Reader"); // Displays "Hello Reader"
hello(); // Displays "Hello World“

Function return type
• In PHP functions even if you don’t return a value, PHP will still
cause your function to return NULL. So there is no concept of
‘void’

Strings
Char a*+=‚Baabtra‛;
Printf(‚Hello %s‛,a);
$a=‚Baabtra‛;
echo ‚Hello $a‛; //Output: Hello baabtra;
echo ‘Hello $a’; //Outputs : Hello $a
‚Strings will be continued in coming
chapters‛
C PHP

Arrays
Indexed Array
int a[]={1,2,3,4,5,6,7,8,9,10};
for(i=0;i<10;i++)
Printf(‚%d‛,a[i]);
Indexed Array / Enumerated array
$a=array(1,2,3,4,5,6,7,8,9,10)
for($i=0;$i<10;$i++)
echo $a[$i] ;
Associative Array
$a*‘name’+=‚John‛;
$a*‘age’+=24;
$a*‘mark’+=35.65;
‚Array will be continued in coming
chapters‛
C PHP

Operators
C
Arithmetic Operators
+, ++, -, --, *, /, %
Comparison Operators
==, !=, ===, !==, >, >=, < , <=
Logical Operators
&&, ||, !
Assignment Operators
=, +=, -=, *=, /=, %=
PHP
‚Supports all on left . In addition
PHP supports below operators as well‛
• Execution Operators
• String operators
• Type Operators
• Error Control Operators
• Bitwise Operators

• The backtick operator makes it possible to execute a shell command and
retrieve its output. For example, the following will cause the output of the
UNIX ls commandto be stored inside $a:
Eg : $a = ‘ls -l‘;
Execution operator (‘)
Don’t confuse the backtick operator with regular quotes (and, conversely, don’t
confuse the latter with the former!)

– The dot (.) operator is used to concatenate two strings
Eg1: $string=‚baabtra‛. ‚mentoring parner‛
Eg2: $string1=‚baabtra‛;
$string2=‚mentoring parner‛;
$string3=$string1.$string2;
String operators (.)

– Used to determine whether a variable is an instantiated object of a certain class or
an object of a class that inherits from a parent class
Eg: class ParentClass
{ }
class MyClass extends ParentClass
{ }
$a = new MyClass;
var_dump($a instanceof MyClass); // returns true as $a is an object of MyClass
var_dump($a instanceof ParentClass); // returns true as $a is an object of MyClass
which inherits parentClass
Type operators (instanceof )

Error suppression operator (@)
• When prepended to an expression, this operator causes PHP to ignore
almost all error messages that occur while that expression is being evaluated
Eg: $x = @mysql_connect(‘localhost’,’root’,’1234’);
• The code above will prevent the call to mysql_connect() from outputting an
error—provided that the function uses PHP’s own functionality for
reporting errors.
• Sadly, some libraries output their errors directly, bypassing PHP and,
therefore, make it much harder to manage with the error-control operator.

• Bitwise operators allow you to manipulate bits of data. All these operators are
designed to work only on integer numbers—therefore, the interpreter will attempt
to convert their operands to integers before executing them.
Bitwise Operators
& Bitwise AND. The result of the operation will be a value whose bits are set if they are set in
both operands, and unset otherwise.
| Bitwise OR. The result of the operation will be a value whose bits are set if they are set in
either operand (or both), and unset otherwise.
ˆ Bitwise XOR (exclusive OR). The result of the operation will be a value whose bits are set if
they are set in either operand, and unset otherwise.
<< Bitwise left shift. This operation shifts the left-hand operand’s bits to the left by a number of
positions equal to the right operand, inserting unset bits in the shifted positions
>> Bitwise right shift. This operation shifts the left-hand operand’s bits to the right by a number
of positions equal to the right operand, inserting unset bits in the shifted positions.

Questions?
‚A good question deserve a good grade…‛

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