common.php

<?php

    // These variables define the connection information for your MySQL database
    $username = "root";
    $password = "";
    $host = "localhost";
    $dbname = "website";

    // UTF-8 is a character encoding scheme that allows you to conveniently store
    // a wide varienty of special characters, like ¢ or €, in your database.
    // By passing the following $options array to the database connection code we
    // are telling the MySQL server that we want to communicate with it using UTF-8
    // See Wikipedia for more information on UTF-8:
    // http://en.wikipedia.org/wiki/UTF-8
    $options = array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8');

    // A try/catch statement is a common method of error handling in object oriented code.
    // First, PHP executes the code within the try block.  If at any time it encounters an
    // error while executing that code, it stops immediately and jumps down to the
    // catch block.  For more detailed information on exceptions and try/catch blocks:
    // http://us2.php.net/manual/en/language.exceptions.php
    try
    {
        // This statement opens a connection to your database using the PDO library
        // PDO is designed to provide a flexible interface between PHP and many
        // different types of database servers.  For more information on PDO:
        // http://us2.php.net/manual/en/class.pdo.php
        $db = new PDO("mysql:host={$host};dbname={$dbname};charset=utf8", $username, $password, $options);
    }
    catch(PDOException $ex)
    {
        // If an error occurs while opening a connection to your database, it will
        // be trapped here.  The script will output an error and stop executing.
        // Note: On a production website, you should not output $ex->getMessage().
        // It may provide an attacker with helpful information about your code
        // (like your database username and password).
        die("Failed to connect to the database: " . $ex->getMessage());
    }

    // This statement configures PDO to throw an exception when it encounters
    // an error.  This allows us to use try/catch blocks to trap database errors.
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // This statement configures PDO to return database rows from your database using an associative
    // array.  This means the array will have string indexes, where the string value
    // represents the name of the column in your database.
    $db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);

    // This block of code is used to undo magic quotes.  Magic quotes are a terrible
    // feature that was removed from PHP as of PHP 5.4.  However, older installations
    // of PHP may still have magic quotes enabled and this code is necessary to
    // prevent them from causing problems.  For more information on magic quotes:
    // http://php.net/manual/en/security.magicquotes.php
    if(function_exists('get_magic_quotes_gpc') && get_magic_quotes_gpc())
    {
        function undo_magic_quotes_gpc(&$array)
        {
            foreach($array as &$value)
            {
                if(is_array($value))
                {
                    undo_magic_quotes_gpc($value);
                }
                else
                {
                    $value = stripslashes($value);
                }
            }
        }

        undo_magic_quotes_gpc($_POST);
        undo_magic_quotes_gpc($_GET);
        undo_magic_quotes_gpc($_COOKIE);
    }

    // This tells the web browser that your content is encoded using UTF-8
    // and that it should submit content back to you using UTF-8
    header('Content-Type: text/html; charset=utf-8');

    // This initializes a session.  Sessions are used to store information about
    // a visitor from one web page visit to the next.  Unlike a cookie, the information is
    // stored on the server-side and cannot be modified by the visitor.  However,
    // note that in most cases sessions do still use cookies and require the visitor
    // to have cookies enabled.  For more information about sessions:
    // http://us.php.net/manual/en/book.session.php
    session_start();

    // Note that it is a good practice to NOT end your PHP files with a closing PHP tag.
    // This prevents trailing newlines on the file from being included in your output,
    // which can cause problems with redirecting users.