When connecting, the pconnect wolud first try to find a (persistent) link that’s already open with the same host, username and password. If the link already exist then the identifier for that will be returned instead of opening a new connection. Later, create a new link for each connection.

The Connection to the SQL server will not be closed when the execution of the script ends. Instead the link will be opened for future use and mysql_close() will not will not close links established by mysql_pconnect(). Later, The link to the server will be closed as soon as the execution of the script ends, unless its closed earlier by explicitly calling mysql_close().

Reference: mysql_pconnect() and mysql_connect()

*To dump data or structure in the database from a dump file

$psql -u DBUserName datbaseName < databaseName_dump.sql

*To take the dump from the database

$pg_dump -u databaseName > filename.sql // data + structure
It will ask the username and password of database

$pg_dump -u databaseName -a > filename.sql // only data

$pg_dump -u databaseName -s > filename.sql // only structure

$pg_dump –username=sql-ledger -W databaseName > filename.sql
It will ask the password of database

To know the ip address of the machine
$ifconfig

To view list of previously typed commands in command prompt
$history | grep <word that need to be searched>

To Know the ip address of the website
$host site-name

To list all the process running in a machine
$ps aux

To kill a process that is running
$kill -9 the process code

To know which process consumes more space
$top

To know how much space the folder occupies
$du -sh .

Ground Floor and First Floor duplex model
Anna Nagar, Chennai, Tamil Nadu
Bedrooms : 3
Land Area : 1200 Sq-ft
Buildup Area – 2000 Sq ft

Description:
This flat is located in Vellacherri, chennai with good surroundings, with spacious rooms, with good water supply, with main road approach, with easy access.

Key Features:-
Semi Furnished, Spaceous terrace, Double Car Parking

Contact Person : Mr. Prathab
Contact Number : +91-9944168941

Let us see how javascript, php, and ruby display the content of textarea with line breaks

Javascript:

document.getElemnetById(‘textareacontent’).value.replace(/\n/g,’<br>’);

PHP:

preg_replace(“/\n/”,”<br>”,$_REQUEST['t1']);

Ruby:

(teaxtareacontent).gsub(/\n/,”<br>”)

The singleton pattern is a design pattern that is used to restrict instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system.

Here is an example, that demonstrates this singleton pattern:

<?php

echo ” 1: “;
$user_1 = CurrentUser::singleton();

echo “\n 2: “;
$user_1->counter();

echo “\n 3: “;
$user_2 = CurrentUser::singleton();

echo “\n 4: “;
$user_2->counter();

echo “\n 5: “;
$user_1->counter();

echo “\n 6: “;
$post = new Post();

echo “\n 7: “;
$post->counter();

/* Singleton Class: CurrentUser */
class CurrentUser
{
// Hold an instance of the class
private static $instance;
private $counter = 0;

// A private constructor; prevents direct creation of object
private function __construct()
{
echo “Constructing CurrentUser \n”;
}

// The singleton method
public static function singleton()
{
if (!isset(self::$instance)) {
$c = __CLASS__;
self::$instance = new $c;
} else {
echo “<span class=\”ghost\”>CurrentUser already exists</span> \n”;
}
return self::$instance;
}

public function counter()
{
echo “CurrentUser -> counter = ” . $this->counter . ” \n”;
++$this->counter;
}
}

/* Normal Class: Post */
class Post
{
private $current_user;

public function __construct()
{
echo “Constructing Post \n “;
$this->current_user = CurrentUser::singleton();
}

public function counter()
{
echo “Post -> counter \n “;
$this->current_user->counter();
}
}
?>

In this code there is a class CurrentUser, which consists of one private and static variable to hold current user object and another private variable for counter.

This class consists of three functions,
1: The contructor – which is called when the class is instantiated
2: Singleton – it checks if the variable instantiate is set or not. If its not set then new object is created else it uses the existing object
3: Counter fn – to increment the counter variable.

Output of the code:
1: Constructing CurrentUser
2: CurrentUser -> counter = 0
3: CurrentUser already exists
4: CurrentUser -> counter = 1
5: CurrentUser -> counter = 2
6: Constructing Post
CurrentUser already exists
7: Post -> counter
CurrentUser -> counter = 3

Here is an example, without singleton pattern

<?php
echo “1: “;
$user_1 = CurrentUser::singleton();

echo “<br>2: “;
$user_1->counter();

echo “<br>3: “;
$user_2 = CurrentUser::singleton();

echo “<br>4: “;
$user_2->counter();

echo “<br>5: “;
$user_1->counter();

echo “<br>6: “;
$post = new Post();

echo “<br>7: “;
$post->counter();

/* Singleton Class: CurrentUser */
class CurrentUser
{
// Hold an instance of the class
private $instance;
private $counter = 0;

// A private constructor; prevents direct creation of object
private function __construct()
{
echo “Constructing CurrentUser \n”;
}

// The singleton method
public function singleton()
{
$c = __CLASS__;
$instance = new $c;
return $instance;
}

public function counter()
{
echo “CurrentUser -> counter = ” . $this->counter . ” \n”;
++$this->counter;
}
}

/* Normal Class: Post */
class Post
{
private $current_user;

public function __construct()
{
echo “Constructing Post <br>”;
$this->current_user = CurrentUser::singleton();
}

public function counter()
{
echo “Post -> counter<br>”;
$this->current_user->counter();
}
}
?>

In this example, the CurrentUser object is created each time when the singleton function is called.

The output of this code:
1: Constructing CurrentUser
2: CurrentUser -> counter = 0
3: Constructing CurrentUser
4: CurrentUser -> counter = 0
5: CurrentUser -> counter = 1
6: Constructing Post
Constructing CurrentUser
7: Post -> counter
CurrentUser -> counter = 0

Reference: Implementing a PHP Singleton

To take dump of whole database:
$ mysqldump -u <username> -p <databasename> > <filename>.sql

To take dump of the (only)structure of the database
$ mysqldump -u <username> -p <databasename> -d > <filename>.sql

To take dump of the (only)data of the database
$ mysqldump -u <username> -p <databasename> -t > <filename>.sql

To take dump of the database with complete insert statement
$ mysqldump -u <username> -p <databasename> -c > <filename>.sql

To create database from command prompt. Login to mysql as root user.
To login into mysql prompt in linux machine.
Type the following command in the console

$ mysql -u <username> -p<password>

After entering the mysql prompt follow these steps to create a database
and load the database with sql file.

A CREATE DATABASE statement to create a database.
> create database <databasename>;

A GRANT statement to grant privileges to database.
> grant all on <databasename>.* to <username>@localhost identified by ‘<password>’;

A FLUSH PRIVILEGES statement to tell the server to reload the grant.
> flush privileges;

A USE statement to tell the server to use the given database for further operations.
> use <databasename>;

A SOURCE statement to tell server to load the given sql file in the database.
> source <filename.sql>

Microformats are tiny little markup definitions built on top of, usually, HTML or XHTML.

The available microformats are hCalendar, hReview, hCard, RelLicense, RelTag, XFN Format etc.,

The basic format of hCard is to use vCard object/property names in lower-case for class names, and to map the nesting of vCard objects directly into nested XHTML elements.

For example, Here is a sample vCard

BEGIN:VCARD
VERSION:3.0
FN:Jeffrey Thomas
END:VCARD

and an equivalent in literal hCard:
< p class=”vcard”> < span class=”fn”>Jeffrey Thomas < \span > < \ p>

There are several ruby parser for parsing this microformats to mention a few like mofo, hpricot etc

Check the microformats wiki for further details.

Importance of Microformats

Helps in – Aggregation Sites and Sharing Information with a Specific Community

You can also get more information from this blog about microformats and how websites using this.