Php introduction

PHP
Krishna priya
April 19, 2011
C-DAC, Hyderabad

What is PHP?
PHP == ‘Hypertext Preprocessor’
Open-source, server-side scripting
language
Used to generate dynamic web-pages
PHP scripts reside between reserved PHP
tags
This allows the programmer to embed PHP
scripts within HTML pages

What is PHP (cont’d)
Interpreted language, scripts are parsed at runtime rather than compiled beforehand
Executed on the server-side
Source-code not visible by client
‘View Source’ in browsers does not display the PHP code

Various built-in functions allow for fast
development
Compatible with many popular databases
including MySQL, PostgreSQL, Oracle, Sybase,
Informix, and Microsoft SQL Server.

Brief History of PHP
PHP (PHP: Hypertext Preprocessor) was created
by Rasmus Lerdorf in 1994. It was initially
developed for HTTP usage logging and serverside form generation in Unix.
PHP 2 (1995) transformed the language into a
Server-side embedded scripting language. Added
database support, file uploads, variables, arrays,
recursive functions, conditionals, iteration,
regular expressions, etc.
PHP 3 (1998) added support for ODBC(Open
Database Connectivity) data sources, multiple
platform support, email protocols and new parser
written

Brief History of PHP (cont’d)
PHP 4 (2000) became an independent component
of the web server for added efficiency. The parser
was renamed the Zend Engine. Many security
features were added.
PHP 5 (2004) adds Zend Engine II with object
oriented programming, robust XML support,
SOAP extension for interoperability with Web
Services, SQLite(SQLite is an embedded database
library that implements a large subset of the SQL
92 standard.) has been bundled with PHP

Advantages of selecting PHP for
Web Development
1. It can be easily embedded into the HTML code.
2. There is no need to pay for using PHP to develop web applications and
websites.
3. It provides support to almost all operating systems that include Windows,
Linux, Mac, etc.
4. Implementing PHP is much easier than other programming languages like
Java, Asp.net, C++, etc.
5. PHP provides compatibility to all web browsers. Be it Internet Explorer,
Mozilla Firefox, Netscape, Google Chrome, Opera, or any other Web
browser, PHP supports all.
6. PHP is compatible with web servers like Apache, IIS, etc.
7. PHP Web development is highly reliable and secure because of the security
features that PHP offers.
8. Provides support to all database servers, such as MSSQL, Oracle, and
MySQL. Because it provides supports for almost all database servers, it is
highly used in developing dynamic web applications.
9. It is the best choice to develop small as well as large websites like
ecommerce websites, discussion forums, etc.
10. It offers flexibility, scalability, and faster speed in comparison to other
scripting languages being used to develop websites.

PHP Environment Setup
In order to develop and run PHP Web
pages three vital components need to be
installed on your computer system.
Web Server, Database , PHP Parser
Wamp Server is an open source project
http://www.wampserver.com/en/dow
nload.php
Wamp Server Version 2.0
PHP:5.2.5, Apache:2.2.6,
MYSQL:5.0.45

How PHP works
When a user navigates in his/her browser to a page that ends
with a .php extension, the request is sent to a web server, which
directs the request to the PHP interpreter.

What does PHP code look like?
Structurally similar to C/C++
Here some similarities and differences in PHP and
C:
Similarities:
Broadly speaking, PHP syntax is the same as in
C:
statements are terminated with semicolons,
function calls have the same structure
(my_function(expression1, expression2)), and curly
braces ({ and }) make statements into blocks.
PHP supports C and C++-style comments (/* */ as well
as //), and also Perl and shell-script style (#).

Similarities(cont’d)
Operators:
The assignment operators (=, +=, *=, and so on),
Boolean operators (&&, ||, !)
the comparison operators (<,>, <=, >=, ==, !=), and
the basic arithmetic operators (+, -, *, /, %) all behave
in PHP as they do in C.

Control structures:
The basic control structures (if, switch, while, for)
behave as they do in C, including supporting break and
continue.
One notable difference is that switch in PHP can accept
strings as case identifiers.

Similarities (cont’d)
Function names:
As you peruse the documentation, you all see
many function names that seem identical to C
functions.

Differences:
Dollar signs:
All variables are denoted with a leading $.
Variables do not need to be declared in
advance of assignment

Differences compare to C
Types:
PHP has only two numerical types: integer
(corresponding to a long in C) and double
(corresponding to a double in C). Strings are of arbitrary
length. There is no separate character type.

Arrays:
Arrays have a syntax superficially similar to C's array
syntax, but they are implemented completely differently.
They are actually associative arrays or hashes, and the
index can be either a number or a string. They do not
need to be declared or allocated in advance.

No structure type:
There is no struct in PHP

No pointers:
There are no pointers available in PHP.
PHP does support variable references. You can
also emulate function pointers to some extent,
in that function names can be stored in
variables and called by using the variable
rather than a literal name.

No prototypes:
Functions do not need to be declared before
their implementation is defined, as long as the
function definition can be found somewhere in
the current code file or included files.

PHP Language Basics
Structurally similar to C/C++
All PHP statements end with a semi-colon
Each PHP script must be enclosed in the reserved
PHP tag
PHP Tag Styles as follows:
<?php
…
?>

short-open tag
<?...?>

ASP-style tags
<%...%>

HTML script tags
<script language="PHP">...</script>

Comments in PHP
There are two commenting formats in
PHP:
1. Single-line comments
2. Multi-lines comments
// C++ and Java-style comment
# This is the second line of the comment
/* C-style comments
These can span multiple lines */

PHP Variables
PHP variables must begin with a “$” sign
Case-sensitive ($Foo != $foo != $fOo)
Certain variable names reserved by PHP
For Example Form variables ($_POST,
$_GET) Etc.
<?php
$foo = 25;
$bar = “Hello”;

// Numerical variable
// String variable

$foo = ($foo * 7); // Multiplies foo by 7
?>

PHP Variable Naming Conventions
There are a few rules that you need to follow when
choosing a name for your PHP variables.
PHP variables must start with a letter or underscore "_".
PHP variables may only be comprised of alpha-numeric
characters and underscores. a-z, A-Z, 0-9, or _ .
Variables with more than one word should be separated
with underscores. $my_variable
Variables with more than one word can also be
distinguished with capitalization. $myVariable

Echo
The PHP command ‘echo’ is used to output the parameters passed
to it
Strings in single quotes (‘ ’) are not interpreted or evaluated by
PHP
<?php
$foo = 25;
$bar = “Hello”;
echo
echo
echo
echo
echo
?>

// Numerical variable
// String variable

$bar;
// Outputs Hello
$foo,$bar; // Outputs 25Hello
“5x5=”,$foo;
// Outputs 5x5=25
“5x5=$foo”; // Outputs 5x5=25
‘5x5=$foo’; // Outputs 5x5=$foo

Notice how echo ‘5x5=$foo’ outputs $foo rather than replacing it with 25
Strings in single quotes (‘ ’) are not interpreted or evaluated by PHP

Concatenation
Use a period to join strings into one.
<?php
$string1=“Hello”;
$string2=“PHP”;
$string3=$string1 . “ ” . $string2;
echo $string3;
?>

Hello PHP

Escaping the Character
If the string has a set of double quotation marks that must remain visible, use
the [backslash] before the quotation marks to ignore and display them.
<?php
$heading=“”Computer Science””;
Print $heading;
?>

“Computer Science”

Operators Examples
Assume variable A holds 10 and variable B holds 20 then:
Type

Operator

Description

Example

Arithmetic

+

Adds two operands

A + B will give 30

Comparision

==

Checks if the value of two
operands are equal or not,
if yes then condition
becomes true.

(A == B) is not
true.

Logical (or Relational)
Operators

and

If both the operands are
true then then condition
becomes true.

(A and B) is true.

Assignment Operators

+=

It adds right operand to
the left operand and
assign the result to left
operand

C += A is
equivalent to C =
C+A

Conditional (or ternary)
Operators

?:

Conditional Expression

If Condition is
true ? Then value
X : Otherwise
value Y

PHP Decision Making
The if, else …elseif and switch statements
are used to take decision based on the
different condition.
<?php
$my_name = "someguy";
if ( $my_name == "someguy" )
{
echo "Your name is
someguy!<br />";
}
echo "Welcome to my
homepage!";
?>
No THEN in PHP

<?php
If($user==“John”)
{
Print “Hello John.”;
}
Else
{
Print “You are not
John.”;
}
?>

PHP Loop Types
Loops in PHP are used to execute the same block of code a
specified number of times. PHP supports following four loop
types.
While

while - loops through a block of code if and as
long as a specified condition is true.

do...while

do...while - loops through a block of code once,
and then repeats the loop as long as a special
condition is true.

for – loop

for - loops through a block of code a specified
number of times.

foreach

foreach - loops through a block of code for each
element in an array.

PHP Arrays
An array stores one or more similar type of
values in a single value.
An array is a special variable, which can store
multiple values in one single variable.
In PHP, there are three kind of arrays:
Numeric array - An array with a numeric index
Associative array - An array where each ID key is
associated with a value
Multidimensional array - An array containing one
or more arrays

Looping through Arrays
Looping through element values
Looping through keys and values

foreach ( $array as $value ) {
// Do stuff with $value
}

foreach ( $array as $key => $value ) {
// Do stuff with $key and/or $value
}

Sorting an Array in PHP
You can sort an array in PHP by using two functions:
sort(), to sort an array in ascending order
rsort(), to sort an array in the reverse order, or descending order

Date Display
$datedisplay=date(“yyyy/m/d”);
echo $datedisplay;

2011/4/19

Tuesday, April 19, 2011

Tue

$datedisplay=date(“l, F m, Y”);
echo $datedisplay;

$date display=date(“D”);
echo $d

Functions
PHP functions are similar to other programming languages. A
function is a piece of code which takes one more input in the form
of parameter and does some processing and returns a value.
There are two parts which should be clear to you:
Creating a PHP Function
Calling a PHP Function

function functionName()
{
code to be executed;
}

PHP File Inclusion
You can include the content of a PHP file into another PHP
file before the server executes it. There are two PHP
functions which can be used to included one PHP file into
another PHP file.
The include() Function
The require() Function
This is a strong point of PHP which helps in creating functions,
headers, footers, or elements that can be reused on multiple pages.
This will help developers to make it easy to change
the layout of complete website with minimal effort.
If there is any change required then instead of changing
thausand of files just change included file.

Php introduction

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