PHP Interview Questions And Answers

What's PHP ?
The PHP Hypertext Preprocessor is a programming language that allows
web developers to create dynamic content that interacts with
databases. PHP is basically used for developing web based software
applications.

What Is a Session?
A session is a logical object created by the PHP engine to allow you
to preserve data across subsequent HTTP requests.

There is only one session object available to your PHP scripts at any
time. Data saved to the session by a script can be retrieved by the
same script or another script when requested from the same visitor.

Sessions are commonly used to store temporary data to allow multiple
PHP pages to offer a complete functional transaction for the same
visitor.

What is meant by PEAR in php?
Answer1:
PEAR is the next revolution in PHP. This repository is bringing higher
level programming to PHP. PEAR is a framework and distribution system
for reusable PHP components. It eases installation by bringing an
automated wizard, and packing the strength and experience of PHP users
into a nicely organised OOP library. PEAR also provides a command-line
interface that can be used to automatically install "packages"

Answer2:
PEAR is short for "PHP Extension and Application Repository" and is
pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-sourced code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP
The PHP Foundation Classes (PFC),
The PHP Extension Community Library (PECL),
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project with the PEAR Group as the
governing body. The project has been founded by Stig S. Bakken in 1999
and quite a lot of people have joined the project since then.

How can we know the number of days between two given dates using PHP?
Simple arithmetic:

$date1 = date('Y-m-d');
$date2 = '2006-07-01';
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo "Number of days since '2006-07-01': $days";
What is the difference between $message and $$message?
Anwser 1:
$message is a simple variable whereas $$message is a reference
variable. Example:
$user = 'bob'

is equivalent to

$holder = 'user';
$$holder = 'bob';

Anwser 2:
They are both variables. But $message is a variable with a fixed name.
$$message is a variable who's name is stored in $message. For example,
if $message contains "var", $$message is the same as $var.

What Is a Persistent Cookie?
A persistent cookie is a cookie which is stored in a cookie file
permanently on the browser's computer. By default, cookies are created
as temporary cookies which stored only in the browser's memory. When
the browser is closed, temporary cookies will be erased. You should
decide when to use temporary cookies and when to use persistent
cookies based on their differences:
*Temporary cookies can not be used for tracking long-term information.
*Persistent cookies can be used for tracking long-term information.
*Temporary cookies are safer because no programs other than the
browser can access them.
*Persistent cookies are less secure because users can open cookie
files see the cookie values.

What does a special set of tags <?= and ?> do in PHP?
The output is displayed directly to the browser.