Database-Enabled Web Applications.! Introduction to PHP! Connecting to IBM DB2 with PHP

Transcription

1 Database-Enabled Web Applications! Introduction to PHP! Connecting to IBM DB2 with PHP

2 Interfacing a Database to the Web! Classical client/server architecture: " server program waits for requests " clients request connections " once the connection is established, the client can send queries/transactions to the server " server processes queries and transactions and returns results to respective clients! DBMS-backed web application: " DBMS client is the web server program " web server receives requests from web clients, and establishes connection to the DBMS server " web server uses some middleware software (e.g. Perl/CGI) for communicating with the database " DBMS server processes requests and sends results back to the web server, which forwards them to the web client client 1 client 2 client n DBMS Server Program Svetlana Vinnik, WS03/04 - Information Systems 2 SQL query results Classical Client-Server Architecture Web client Web server Perl/CGI CGI DBMS Server Program Oracle Client/ Server Protocol Web-server-as-DB-client Architecture

3 Databases on the Web Overview of Technologies! A dynamic Web page is a page that interacts with the user, so that each user visiting the page sees customized information.! Dynamic Web applications are prevalent in e-commerce sites and search engines, where the content displayed is generated from information accessed in a database or other external source.! Some popular technologies and standards for building database-enabled applications ale listed below: ODBC (Open DataBase application programming interface for database access Connectivity) JDBC (Java DataBase Connectivity) Perl/CGI(Common Gateway Interface) ASP (Active Server Pages) PHP (Hypertext Preprocessor) cross-dbms connectivity to a wide range of SQL databases and other tabular sources the most widely used language for writing server-side component modules standard technology used to create dynamic web content on Microsoft web servers cross-platform web application development environment with easy-to-use features for integrating with databases Svetlana Vinnik, WS03/04 - Information Systems 3

4 Open DataBase Connectivity Abstracting Application from a Database Open DataBase Connectivity (ODBC) is an Application Programming Interface that allows a programmer to abstract a program from a database. Advantages provided by ODBC:! ODBC API is independent of any specific DBMS or operating system! accessing different DBMSs with the same source code without recompiling! accessing multiple DBMSs simultaneously! The developers of DBMS-specific drivers implement the ODBC interface! Applications use these drivers to access data in a DBMS-independent manner! applications supporting ODBC recognize a common subset of SQL statements! A Driver Manager manages communication between applications and drivers Databases that support ODBC MySQL, IBM DB2, Informix, MS Access, MS SQL Server, Cold Fusion, Paradox, MS Dbase, FoxPro, Oracle, Sybase, Primebase, PostgreSQL, OpenBase, Kubl, CQL++, MimerSQL, SOLID, MiniSQL, DBIX, LNX-DBMS, Cache, Interbase etc. Svetlana Vinnik, WS03/04 - Information Systems 4

5 Basic ODBC Application Steps! Interaction with a database server from any ODBC application involves basically the following steps of operations: " Configuring the ODBC DSN (connection details required to login) " Connecting to the database server " Initializations " Preparation of SQL statements (optional) " Execution of SQL statements " Retrieving results " Performing Transactions " Disconnecting from the server Svetlana Vinnik, WS03/04 - Information Systems 5

6 Welcome to PHP! PHP (Hypertext Preprocessor) is an open-source server-side, HTML-embedded, cross-platform scripting language (freely downloadable from General idea:! provides a way to put instructions in HTML code to create dynamic content! PHP instructions are read and parsed by the web server (not by the browser that is displaying the page!)! The web server replaces PHP code with the content generated by that code! provides a wide variety of functions that support everything from array manipulation to regular expressions Svetlana Vinnik, WS03/04 - Information Systems 6

7 What makes PHP so attractive PHP is today's fastest-growing technology for dynamic Web pages: " a simple universal solution for easy-to-program dynamic Web pages " PHP commands are embedded right in the HTML page " PHP's syntax is similar to that of C, Java, and Perl " extremely simple for a newcomer, but offers many advanced features for a professional programmer " offers high code performance " enjoys the support of a large group of open-source developers " excellent technical support, bugs are found and repaired quickly " code is continuously updated with improvements and language extensions to expand PHP's capabilities Svetlana Vinnik, WS03/04 - Information Systems 7

8 What can PHP do?! server-side scripting (collect form data, generate dynamic page content, or send and receive cookies, and much more)! command line scripting (for example, simple text processing tasks )! build database-enabled web pages! outputting images, PDF files, Flash movies etc. generated on the fly! support for talking to other services using protocols such as LDAP, IMAP, SNMP, NNTP, POP3, HTTP, COM etc.! support for instantiation of Java objects and using them as PHP objects! CORBA extension to access remote objects! useful text processing features, from regular expressions to parsing XML documents! search engine functions, many compression utilities, calendar conversion, translation, Svetlana Vinnik, WS03/04 - Information Systems 8

9 Introductory Example! To call a PHP-function, embed it within the HTML source! PHP uses HTML-style tags that begin with <?php and end with?>! PHP-statements are separated by semicolons! you do not need a semicolon terminating the last line of a PHP block <html> <head> <title>example</title> </head> <body> <?php echo "Hi, I am a PHP script!"; echo "<BR>And who are you?"?> </body> </html> Svetlana Vinnik, WS03/04 - Information Systems 9

10 PHP Basics - Comments! PHP supports 'C', 'C++' and Unix shell-style comments. Here are some examples: <?php echo "This is a test"; //a one-line C++ style comment /* This is a multi-line comment yet another line of comment */ echo "This is yet another test"; echo "One Final Test"; # This is shell-style style comment?> Svetlana Vinnik, WS03/04 - Information Systems 10

11 PHP Basics - Types! PHP supports eight primitive types. " Four scalar types: boolean (Example: $foo = FALSE;) integer (Example: $a = -123;) floating-point (Example: $a = 1.234;) string (Example: $str = "This is a string";) " Two compound types: array (Example: $b[]='a'; $b[]='b'; $b[]='c';) object (Example: $bar = new MyClass;) " Two special types: resource a variable holding a reference to an external resource ( e.g., database connection identifier) NULL represents that a variable has no value Svetlana Vinnik, WS03/04 - Information Systems 11

12 PHP Basics - Variables! Variables are represented by a dollar sign followed by the name of the variable: $varname.! The variable name is case-sensitive.! PHP does not support explicit type definition in variable declaration! variable's type is determined by the context in which that variable is used (automatic type conversion)! Type casting forces a variable to be evaluated as a certain type: $foo = 10; // $foo is an integer $bar = (float) $foo; // $bar is a float! To change variable s type use settype(): $bar = true; // boolean settype($bar, "string"); // $bar is now "1" (string) Svetlana Vinnik, WS03/04 - Information Systems 12

13 PHP Basics Predefined Variables! PHP provides a large number of predefined variables (dependent upon the server configuration and other factors).! There is a set of predefined arrays containing variables from the web server (such as cookies, posted values, etc.). These arrays automatically global -- i.e., available in every scope.! Some helpful globals are listed below: $HTTP_GET_VARS $HTTP_POST_VARS $_COOKIES $_SESSION Variables provided to the script via HTTP GET Variables provided to the script via HTTP POST Variables provided to the script via HTTP cookies Array for registering user-defined variables in order to make them globally accessible across the session! For example, to make a user-defined variable global, i.e. accessible from any script across the session, register it with $_SESSION: $_SESSION[' counter ']=$counter; Svetlana Vinnik, WS03/04 - Information Systems 13

14 PHP Basics Predefined Variables! When a HTML form is submitted to a PHP script, any values from that form will be automatically made available to that script! These variables are stored in the associative arrays $HTTP_POST_VARS, $HTTP_GET_VARS, and/or $HTTP_POST_FILES! Below is an example of a form asking to enter a password: <form action="foo.php" method="post"> Enter your password: <input type="password" name="pw"> <input type="submit"> </form>! In foo.php, the posted password can be retrieved as follows: <?php $password = $HTTP_POST_VARS['pw']; // further assignments?> Svetlana Vinnik, WS03/04 - Information Systems 14

15 PHP Basics Expressions! PHP is an expression-oriented language, in the sense that almost everything is an expression.! Expressions in PHP are of the same types as in programming languages: assigning values to variables, declaring constants, function calls, increment/decrement, comparisons, etc.! The following code contains some examples of expressions: $exp = 3; $base = 2; $power = pow($base,$exp); //function returning the $base //in the power of $exp, so $power=8 $b = $a = $power; // assign the value of $power, i.e. 8, // to both variables $a and $b $e = $d = ++$b; /* pre-increment, assign the incremented value of $b (9) to $d and $e */ $f = sqrt($d++); /* assign the square root of $d to $f, increment $d afterwards, $f=3, $d=10 */ Svetlana Vinnik, WS03/04 - Information Systems 15

16 PHP Basics Operators! Expressions are combined and manipulated using operators.! PHP operators should be familiar to you if you have any C, Java, or Perl experience.! The table shows the operators available in PHP with their associativity (A). Operators are shown in the descending order of precedence.! PHP has its specific operators, e.g. error control concatenation operator., backticks operator ` ` for specifying shell commands, and others. Operators new [! ~ (int) (float) (string) (array) * / % + -. << >> < <= >= > ==!= ===!== & ^ &&? : (conditional operator) = += -= *= /=.= %= &= = ^= ~= <<= >>= print and xor or A N/A right right left left left N/A N/A left left left left left left left right left left left Svetlana Vinnik, WS03/04 - Information Systems 16

17 PHP Basics Control Structures! Control structures are used to control the logical flow through a PHP script! The control structures in PHP are very similar to those in the C language (but have two interchangeable syntaxes as shown in the example below): " if " else " elseif " while " do while " for " foreach " break " continue " switch //example of 2 syntaxes for a while-loop $i = 1; while ($i <= 10) { print $i++; // the printed value would } //be $i before the increment /* another syntax */ $i = 1; while ($i <= 10): print $i; $i++; endwhile; Svetlana Vinnik, WS03/04 - Information Systems 17

18 PHP Basics Functions! A function is a named sequence of code statements that can optionally accept parameters and return a value.! PHP provides a large number of internal functions.! PHP also supports user-definable functions.! A function may be defined using syntax such as the following: function foo ($arg_1, $arg_2,..., $arg_n) { echo "Example function.\n"; return $retval; }! PHP4 supports variable numbers of arguments to functions.! Parameters are passed to functions via the argument list, which is a comma-delimited list of variables and/or constants.! PHP supports passing arguments by value (the default), passing by reference, and default argument values. Svetlana Vinnik, WS03/04 - Information Systems 18

19 PHP Basics Classes and Objects! The concept of classes and objects, as well as related notions of constructors, inheritance, overloading functions etc. in PHP are borrowed from object-oriented programming languages, such as Java and C++! The below code shows the use of classes and inheritance in PHP class A { //declaring class A function A() { //constructor echo "I am the constructor of A.<br>\n"; } } class B extends A { function foobar() { echo "I am a member function of B.<br>\n"; } } $b = new B; //create B instance with default constructor $b->foobar(); //invoke B s member function Svetlana Vinnik, WS03/04 - Information Systems 19

20 Database Connectivity with PHP! PHP supports a large number of databases natively! Additionally, PHP supports ODBC, so you can connect to any other database packaged with the required ODBC drivers! An existing PHP application can be ported from one database to another by changing just one line (database connection string)! Writing a database-enabled web page is incredibly simple! The following databases are currently supported: Adabas D dbase Empress FilePro (read-only) Ingres InterBase FrontBase msql Oracle (OCI7 and OCI8) Ovrimos PostgreSQL Solid Hyperwave IBM DB2 Informix Direct MS-SQL SQL MySQL ODBC Sybase Velocis Unix dbm Svetlana Vinnik, WS03/04 - Information Systems 20

21 Unified ODBC functions in PHP ODBC support and the Unified ODBC functions are not the same in PHP:! ODBC support is realized through iodbc (Independent ODBC) implemented and maintained by OpenLink Software. Building PHP with iodbc support enables you to use any ODBC-compliant drivers with your PHP applications! Unified ODBC functions do not involve ODBC, but rather speak natively to specific databases and just happen to share the same names and syntax as the ODBC functions. Databases currently supported by the Unified ODBC functions: Adabas D, IBM DB2, iodbc, Solid, and Sybase SQL Anywhere. To access above databases with PHP, install the required libraries. For example, to connect to IBM DB2, install PHP as follows:./configure --without-mysql -with-ibm-db2= / /usr/imbdb2/v7.2/ --with-apache=/usr/local/httpd/ Svetlana Vinnik, WS03/04 - Information Systems 21

22 Step 1: Connecting to the Database! To connect to a specific database, you have to specify a database s name, a valid user name and a password associated with it! Let us first provide a HTML form for entering user login information: <html> <head><title>datenbank Login</title></head> <body> <h3>bitte melden Sie sich an.</h3> <form action="connection.php" method="post"> <p>username <input type="text" name="user"></p> <p>datenbank <select name="db"> <option value="infosys">infosys</option> <option value="moviedb">moviedb</option></select></p> <p><input type=submit value="anmelden"></p> </form> </body> </html> Svetlana Vinnik, WS03/04 - Information Systems 22

23 Step 1: Connecting to the Database! Now, in the connection.php, start a session and attempt to connect to the database with the user name and the password specified: <?php session_start()?> <html> <head><title>datenbankverbindung</title></head> <body> <?php $user=$http_post_vars['user']; $db=$http_post_vars['db']; $connectionid = odbc_connect($db, $user, infosys"); if($connectionid!= 0) { echo "Sie sind als Benutzer <b> $user </b> <br> mit der Datenbank <b> $db </b> verbunden."; odbc_close($connectionid); } else echo "<p>verbindung ist fehlgeschlagen!\n</p>";?> </body> </html> Svetlana Vinnik, WS03/04 - Information Systems 23

24 Step 2: Create an SQL Query! The below script demonstrates how an SQL query can be constructed and passed over to the database for execution: <?php session_start()?> <html> <head><title>executing a query</title></head> <body> <?php $connectionid = odbc_connect("infosys", "nobody", "nobody"); $p1="select actor_id FROM Actor WHERE name='potente, Franka'"; $p2="select film_id from Act_Film WHERE actor_id IN ($p1)"; $query = "SELECT * FROM Film WHERE film_id IN ($p2)"; echo "Your query : $query "; if($result = odbc_exec($connectionid, $query)) odbc_result_all($result); odbc_close($connectionid);?> </body> </html> Svetlana Vinnik, WS03/04 - Information Systems 24

25 Step 3: Formatting the Results! PHP provides functions for retrieving and processing the results of an SQL query, executed with odbc_exec().! Some of those functions are listed below: int odbc_num_fields(resource result_id) int odbc_num_rows(resource result_id) string odbc_field_name(resource result_id, int field) bool odbc_fetch_row(resource result_id [, int row]) string odbc_result(resource result_id, mixed field) string odbc_field_type(resource result_id, int field) returns the number of columns in an ODBC result returns the number of rows in an ODBC result returns the column name under the given column number in an ODBC result fetches the specified row of the data in an ODBC result returns the value of the field specified by name or position returns the SQL type of the field specified Svetlana Vinnik, WS03/04 - Information Systems 25

26 Step 3: Formatting the Results! Here is a PHP code demonstrating the use of the functions introduced in the previous slide for formatting the query result: if($result = odbc_exec($connectionid, $query)) { $columns = odbc_num_fields($result); $rows = odbc_num_rows($result); echo "<p>the query returned $rows entries:"; echo "<table width=90% border=2>"; echo "<tr bgcolor=\"#eaecef\"><th>#</th>"; for($i=1; $i <=$columns; $i++) echo "<th>".odbc_field_name($result, $i)."</th>\n"; echo "</tr>\n<tr>"; $counter=1; while(odbc_fetch_row($result)) { echo "<tr>\n<td>".$counter++."</td>"; for($i=1; $i <=$columns; $i++) echo "<td>".odbc_result($result, $i)."</td>\n"; echo "</tr>\n"; } echo "</tr></table>"; } Svetlana Vinnik, WS03/04 - Information Systems 26

27 Further References! PHP Manual (the official PHP reference) under Unified ODBC functions (Chapter from the above manual) under Using PHP with ODBC A User Guide (somewhat Windows oriented, but contains good examples) under Connecting PHP Applications to IBM DB2 Universal Database (technical article with installation instructions and an example) under ott.html! PHPEveryWhere (a huge PHP portal with lots of useful links) under (PHP portal for German speakers) Svetlana Vinnik, WS03/04 - Information Systems 27

28 Hosting your PHP-scripts! Place the webpages and PHP-scripts you want to execute into the directory /net/www_io/infosys/username! Make sure you set the permissions for your webpages properly (i.e. readable for everybody) $ chmod 644 /net/www_io/infosys/username/*! Now you can make your scripts work by access them through a webbrowser under the following URL: Enjoy your time with PHP! Svetlana Vinnik, WS03/04 - Information Systems 28