DB Programming on the Web COP4710 Database Systems DB Programming on the Web

PHP + MySQL/MariaDB as a case study Introduction Programming Environment Database Programming in the Web Era Web Programming PHP + MySQL/MariaDB as a case study

Motivation Here Comes Another Bubble: http://www.youtube.com/watch?v=I6IQ_FOCE6I Are you feeling “so behind the times”? Closely relevant to your programming project!

What is Internet?

How does the web work? Information is stored in documents called Web pages index.html, index.php, etc. Web pages are files on computers called Web servers Apache, Nginx, IIS, etc. Computers reading the Web pages are called Web clients PCs, Laptops, Phones, Tablets, etc. Web clients view the pages with a program called Web browsers IE, Chrome, and Firefox, Opera, etc.

Key Concepts HTTP: Hyper-Text Transfer Protocol The underlying protocol used by the World Wide Web Defines how messages are formatted and transmitted Defines actions Web servers and browsers should take in response to various commands HTML: Hyper-Text Markup Language Specific standard used for the World Wide Web Can embed scripting languages (e.g. PHP, JavaScript) Interpreted by web browser (client side)

Web Development Tools Client-side: Server-side: HTML: Primary language for creating web pages (page structure) CSS: How HTML elements are to be displayed (page style) JavaScript: Client-side scripting language (browser behavior) …… Server-side: PHP: Server-side scripting language (server behavior) SQL: Standard language for accessing and manipulating databases

LAMP (WAMP) Linux, Apache, MySQL and PHP Linux Apache (www.apache.org) Solution stack of free, open source software Linux Unix-like open source computer operating system Apache (www.apache.org) Open source web server, most popular in use MySQL (www.mysql.com) SQL relational database management system (RDBMS) PHP (www.php.net) Server side scripting language

XAMPP Free Web Server Solution Package Cross-platform (Mac, Windows, Linux, Solaris): http://www.apachefriends.org/en/xampp.html Apache HTTP Server MySQL/MariaDB databases, phpMyAdmin PHP, Perl FileZilla FTP Server …… XAMPP Tutorial: https://www.udemy.com/blog/xampp-tutorial/

XAMPP Install Run Test: http://localhost

How to work? Put your helloworld.php file under xampp/htdocs folder To test your program go to: http://localhost/helloworld.php To check your MySQL database management system go to: http://localhost/phpMyAdmin Create a Webserver on your computer with XAMPP http://www.youtube.com/watch?v=nOe1K3f4gEg&feature=related Create a Database and Table in phpMyAdmin http://www.youtube.com/watch?v=nBz2lG_jm-A

DB Programming SQL is a (very) high-level language Solutions Not intended for general purpose computations Solutions Outside DBMS: use SQL together with general-purpose programming languages, e.g. PHP, etc. Inside DBMS: augment SQL with constructs from general-purpose programming languages

Typical DB Programming Procedure Connect to a DB Server Specify what database you want to use Create a string containing an SQL statement Execute the statement Extract the results into variables in the local programming language Database Specific API Designed and implemented by the DBMS vendor for a specific programming language

MySQL-PHP API - Connection Mysql_connect opens a connection to the DBMS It gets the DBMS and login information and returns a connection resource The connection resource is used in future calls mysqli_connect: new versions of PHP (>5.0) Mysql_select_db selects the desired database Mysql_close closes the connection at the end It is automatically called at the end of the script mysqli_close

Connection - Example MySQL-PHP API:: Connection example in PHP $username = “USERNAME”; $password = “PASSWORD”; $host = “localhost”; $dbname= “DatabaseName”; $connect = mysql_connect($host, $username, $password); mysql_select_db($dbname, $connect); //Do Stuff with the DB Connection mysql_close($connect); PHP: Connect to a MySQL database http://www.youtube.com/watch?v=4rfeWzpszQU

Executing SQL Statement mysql_query(S, C) Causes the SQL statement represented by S to be executed on connection C query mysql_query returns a handle to the query result set TRUE/FALSE for DELETE, UPDATE, and INSERT We can detect DBMS initiated errors using mysql_error()

Executing SQL Statement - Example $query = “SELECT * FROM Beer”; $result = mysql_query($query, $connect); $query = “INSERT INTO Beer (manf, beer) VALUES (“Miller”, “High Life”); ” if (mysql_query($query, $connect)) { echo “Insert Successful”; } else { echo “Insert Failed:”. mysql_error(); }

Fetching Tuples When the SQL statement executed is a query, we need to fetch the tuples of the result mysql_fetch_array(H) gets the tuples from the result set H and stores them in an associative array Mysqli_fetch_array, Mysqli_fetch_assoc mysql_free_result(H) frees the result set It is called automatically at the end of the script Mysqli_free_result

Fetching Tuples: Example $query = “SELECT * FROM Beer”; $result = mysql_query($query, $connect); While ($row = mysql_fetch_array($result)) { $manf= $row[‘manf’]; $beer = $row[‘beer’]; echo “The beer”. $beer . “ is made by”. $manf; } mysql_free_result($result);

Other PHP-MySQL Commands mysql_num_rows(r) Checks the Result handler to see how many rows were returned mysql_affected_rows() Useful on DELETE or UPDATE commands to see how many rows were changed More functions at https://dev.mysql.com/doc/apis-php/en/apis-php-mysqlinfo.html Example: Create a Simple View Counter http://www.youtube.com/watch?annotation_id=annotation_257200&feature=iv&src_vid=4rfeWzpszQU&v=jAKcdxKhiJ8

Web Programming Client Side Programming: Code that runs on the client side’s browser HTML Predominant markup language for web pages Written in the form of HTML elements consisting of "tags" surrounded by angle brackets within the web page content Javascript often implemented as part of a web browser in order to provide enhanced user interfaces and dynamic websites

Web Programming Client Side Programming: Code that runs on the client side’s browser Applet and ActiveX small application that performs one specific task and runs within a larger program E.g. Java Applet running on web pages AJAX (Asynchronous Javascript And XML) To create interactive web applications Using AJAX, web applications can send data and retrieve data from a server asynchronously (in the background)

Web Programming Server Side Programming: Code that runs on the server side CGI: standard protocol for server-client communication PHP: open source ASP.NET: Microsoft proprietary JSP: JavaServer Pages Python, e.g. Django web framework, open source Ruby, e.g. Ruby on Rails, open source ……

HTML Hyper Text Markup Language Tags .html & .htm format – both are correct Interpreted by browser to show elements on the webpage Can contain scripting languages (PHP, javascript, etc.) Tags Keywords surrounded by angle brackets <tag> Tags come in pairs: opening and closing: <tag> </tag> Elements come between these tag: <tag>element</tag> <a href=“http://example.com”>Click here</a> = Click here

HTML Basic Tags <html> </html> <head> </head> Contain all the elements in the page <head> </head> Contain header information such as title, meta data, stylesheets <body> </body> Contains elements that are to be shown on the webpage <h1> … <h6> for headings <img> image

HTML Basic Tags <table> table <tr> table row <td> table data <form> : HTML forms are used to pass data to a server text fields, checkboxes, radio-buttons, submit buttons and etc. $_GET and $_POST methods

HTML Tag Attributes Each tag has attributes Example Attributes provide additional information about the element Should be specified in the opening tag Attribute name = “attribute value” Example <input type=“text” id=“firstname” name=“firstname”> type: specifies the type of <input> element to display id: specifies a unique id for an HTML element can be used by CSS or JavaScript name: specifies the name of an <input> element used to reference from data after a form is submitted

PHP Overview Name comes from Hypertext Preprocessor Originally Personal Home Page Tools (PHP Tools) Open source, server-side, HTML embedded scripting language used to create dynamic Web pages PHP runs on different platforms PHP is compatible with almost all servers used today, such as Apache, IIS PHP files have a file extension of ".php", ".php3", or ".phtml"

PHP Syntax PHP scripting block <?php Script Here ?> Can be place anywhere in the HTML code Can contain HTML tags Script consists of statements and variables Script code should end with semicolon (;) // for single line comment, /* comment */ for multiline comment

PHP Variables Variables are used for storing values, like text strings, numbers or arrays All variables in PHP start with a $ symbol In PHP, a variable does not need to be declared before adding a value to it Variable type is not necessary to be declared $x=16; $txt="Hello World!"; A variable name should not contain spaces. If a variable name is more than one word, it can be separated with an underscore ($my_string)

PHP Variables String concatenation: $a . $b Single quote and double quote are different Variable in double quote is replaced by its value Variable in single quote is shown as it is Example: $email_address = me@domain.com; <?php echo “My email: $email_address”; ?>: displays My email: me@domain.com <?php echo ‘My email: $email_address’; ?>: displays My email: $email_address

$_GET Vs. $_POST $_GET variable is used to collect values in a form with method="get" Information sent from a form with the GET method is visible to everyone and has limits on the amount of information to send $_POST variable is used to collect values from a form sent with method="post" Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send

$_POST Usage <form action="welcome.php" method="post"> Name: <input type="text" name="fname" /> Age: <input type="text" name="age" /> <input type="submit" /> </form> How we use it in PHP: Welcome <?php echo $_POST["fname"]; ?>!<br /> You are <?php echo $_POST["age"]; ?> years old

Take-home Message Web-based DB Programming is not hard but it takes time to learn basics and fix bugs Choose your preferred tools early, and start to get familiar with them Many tutorials (with examples) available on the web W3Schools is a great place to start: http://www.w3schools.com

References Getting starting with CGI Programming in C http://www.cs.tut.fi/~jkorpela/forms/cgic.html PHP related examples, including PHP + MySQL http://www.w3schools.com/php/ W3Schools tutorials are generally very helpful, on almost all the tools we covered Installing, configuring, and developing with XAMPP http://dalibor.dvorski.net/downloads/docs/InstallingConfiguringDevelopingWithXAMPP.pdf Also for using PHP with MySQL Hugh Williams and David Lane, ``Web Database Applications with PHP and MySQL'' 2nd edition