How can we encrypt the username and password using PHP?

You can encrypt a password with the following Mysql>SET
PASSWORD=PASSWORD("Password");

You can use the MySQL PASSWORD() function to encrypt username and password. For
example,
INSERT into user (password, ...) VALUES (PASSWORD($password”)), ...);

What are the different tables present in MySQL?

What are the different tables present in MySQL? Which type of table is generated
when we are creating a table in the following syntax: create table employee(eno
int(2),ename varchar(10))?

Total 5 types of tables we can create
1. MyISAM
2. Heap
3. Merge
4. INNO DB
5. ISAM
MyISAM is the default storage engine as of MySQL 3.23. When you fire the above
create query MySQL will create a MyISAM table.

How can I execute a PHP script using command line?

Just run the PHP CLI (Command Line Interface) program and provide the PHP script file
name as the command line argument. For example, "php myScript.php", assuming "php"
is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may not
execute properly in command line environment.

What is the difference between mysql_fetch_object and mysql_fetch_array?

MySQL fetch object will collect first single matching record where mysql_fetch_array
will collect all matching records from the table in an array

How To Get the Uploaded File Information in the Receiving Script?

Once the Web server received the uploaded file, it will call the PHP script specified in the
form action attribute to process them. This receiving PHP script can get the uploaded file
information through the predefined array called $_FILES. Uploaded file information is
organized in $_FILES as a two-dimensional array as:
· $_FILES[$fieldName]['name'] - The Original file name on the browser system.
· $_FILES[$fieldName]['type'] - The file type determined by the browser.
· $_FILES[$fieldName]['size'] - The Number of bytes of the file content.
· $_FILES[$fieldName]['tmp_name'] - The temporary filename of the file in which
the uploaded file was stored on the server.
· $_FILES[$fieldName]['error'] - The error code associated with this file upload.
The $fieldName is the name used in the 'input name="fieldname" type="FILE,"

What is meant by urlencode and urldecode?

urlencode() returns the URL encoded version of the given string. URL coding converts
special characters into % signs followed by two hex digits. For example:
urlencode("10.00%") will return "10%2E00%25". URL encoded strings are safe to be
used as part of URLs.
urldecode() returns the URL decoded version of the given string.

string urlencode(str) - Returns the URL encoded version of the input string. String values
to be used in URL query string need to be URL encoded. In the URL encoded version:
Alphanumeric characters are maintained as is.
Space characters are converted to "+" characters.
Other non-alphanumeric characters are converted "%" followed by two hex digits
representing the converted character.
string urldecode(str) - Returns the original string of the input URL encoded string.
For example:
$discount ="10.00%";
$url = "http://domain.com/submit.php?disc=".urlencode($discount);
echo $url;
You will get "http://domain.com/submit.php?disc=10%2E00%25".

What are the differences between require and include, include_once?

require_once() and include_once() are both the functions to include and evaluate the
specified file only once. If the specified file is included previous to the present call
occurrence, it will not be done again.

But require() and include() will do it as many times they are asked to do.


The include_once() statement includes and evaluates the specified file during the
execution of the script. This is a behavior similar to the include() statement, with the only
difference being that if the code from a file has already been included, it will not be
included again. The major difference between include() and require() is that in failure
include() produces a warning message whereas require() produces a fatal errors.

All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include() does not.
The include_once() statement includes and evaluates the specified file during the
execution of the script. This is a behavior similar to the include() statement, with the only
difference being that if the code from a file has already been included, it will not be
included again. It des not call a fatal error if file not exists. require_once() does the same
as include_once(), but it calls a fatal error if file not exists.

File will not be included more than once. If we want to include a file once only and
further calling of the file will be ignored then we have to use the PHP function
include_once(). This will prevent problems with function redefinitions, variable value
reassignments, etc.

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 is the difference between $message and $$message?

They are both variables. But $message is a variable with a fixed name. $$message is a
variable who's name is stored in $message.

Example:
$user = 'bob'
is equivalent to
$holder = 'user';
$$holder = 'bob';

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

This is how we calculate the number of days between two given dates using PHP:

$date1 = date('Y-m-d');
$date2 = '2006-07-01';
$days = (strtotime() - strtotime()) / (60 * 60 * 24);
echo "Number of days since '2008-01-01': $days";

What is meant by PEAR in php?

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.

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.

How to Referencing an instance

In PHP 5 objects are passed by reference by default.

class Person{
function say_hello(){
echo "Say hello from inside a clas";
}
function say_hi(){
echo "Say hi";
}
}

$person=new Person();
$person2=new Person();

echo get_class($person)."
";
if(is_a($person2,'Person')){
echo "yes, Its a person";
}
else{
echo "No, Its not a person";
}
$person2->say_hello();
?>

How to define a class method

class Person{
function say_hi(){
echo "Say hi from inside a class";
}
}

$methods=get_class_methods('Person');

foreach($methods as $method){
echo $method . "";
}
?>

Chek if a class name is decleared or not

class Person{

}

if(class_exists("Person")){
echo "The class defined here";
}else{
echo "The class not defined here";
}

?>

Get the name of the all declared classes

class Person {

}

$classes = get_declared_classes();
foreach($classes as $class) {
echo $class ."";
}

What is the main difference between myisam and innodb

Both myisam and innodb are storange enginein sql.
innodb support transaction, foreign key while myisam not
support transaction.
Other differences are :

1. innodb requires more RAM than mysiam
2. myisam relies on OS for caching while innodb caches with
in the engine itself.

3. Most preffered is innodb because

- Transaction safe
-It has commit, rollback, and crash recovery capabailities
- Innodb is designed for maximum performance when processing
large volumes of data.


InnoDB: Row level locking, Transaction support, forgin key
constrant and crash recovery.

MyISAM: Much more conservate approach to disk space
management each MyISAM table store in a separate file. in
MyISAM memory and space usage, full text indexing support,
table based locking, bulk insert capabilities and speed are
plus factor but crushes recovery would be the horror story.

As general approach, if you have a more reads use MyISAM and
if you have a more update use InnoDB.

InnoDb table take More Disk space Comparing with MyISAM
InnoDB is Transactions safe means Data Integrity is
maintained Throughout entire qry process.
InnoDB also provides Row-locking as opposed to table
locking while 1 qry is busy with updating or inserting
arow,another qry can update a different row at the same
time.these features increases the multi user concurrency
and Performance
Another greate feature is InnoDB boasts is the ability to
use Foreign key constraints