1. M.P. Johnson, DBMS, Stern/NYU, Sp20041 C20.0046: Database Management Systems Lecture #21 Matthew P. Johnson Stern School of Business, NYU Spring, 2004

2. M.P. Johnson, DBMS, Stern/NYU, Sp2004 2 Agenda Previously: CGI, Perl Next: Scripting for SQL on the web  More Perl  PHP Security Project part 4 due today Project part 5 assigned today  Short hw?

3. M.P. Johnson, DBMS, Stern/NYU, Sp2004 3 Review: CGI Program Client Server HTTP Request Data for program Generated HTML HTML Image from http://www.scit.wlv.ac.uk/~jphb/cp3024/

4. M.P. Johnson, DBMS, Stern/NYU, Sp2004 4 Perl and HTML headers Data sent to a browser is prefaced with a header describe type of data: Hand-generated html must print this before anything else: Or:  When use-ing CGI Content-type: text/html\n\n print “Content-type: text/html\n\n”; print CGI::header();

5. M.P. Johnson, DBMS, Stern/NYU, Sp2004 5 Perl, HTML, and CGI.pm CGI.pm offers a “front-end” to HTML  Replaces mark-up language with an API Very simple example:  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.cgi Somewhat simpler, but another thing to learn Mostly won’t cover Review: Hello, World

6. M.P. Johnson, DBMS, Stern/NYU, Sp2004 6 New topic: HTML forms “Active” parts of HTML: forms Intuition for name: paper form  Fill in textboxes, check boxes or not, etc.  Turn it in HTML form  contains arb. # of INPUTs  Submits to somewhere (ACTION)  By GET or POST

7. M.P. Johnson, DBMS, Stern/NYU, Sp2004 7 Form example (visible?) From http://www.zend.com/zend/art/art-sweat4.php On clicking Send, we go to script.php with “foo=bar” http://pages.stern.nyu.edu/~mjohnson/dbms/perl/input.cgi

8. M.P. Johnson, DBMS, Stern/NYU, Sp2004 8 Perl and forms Obtain param number: Goal: display text and button;  On submit, tell user what was entered http://pages.stern.nyu.edu/~mjohnson/dbms/perl/inputcgi.txt Improve: also print, say, double the input my $cgi = CGI->new(); $param = $cgi->param('number'); my $cgi = CGI->new(); $param = $cgi->param('number');

9. M.P. Johnson, DBMS, Stern/NYU, Sp2004 9 Perl error-handling Many Perl scripts have lines of the form  some-statement OR die(“something happened”); What this means:  die exits with error message  Perl supports both || and OR as or operator  Perl supports boolean “short-circuiting” Boolean eval stops as fast as possible  Ftns often return 0/null/false for errors  if some-statement fails then we die

10. M.P. Johnson, DBMS, Stern/NYU, Sp2004 10 Perl and databases DB connectivity is done through DBI  Database Interface  Analogous to Java’s JDBC Think of DBI as a Java class with static methods Use these to obtain a connection, prepare and execute queries, etc.

11. M.P. Johnson, DBMS, Stern/NYU, Sp2004 11 Perl DBI 1. Open a connection: 2. Prepare and execute query: my $dbh = DBI-> connect("dbi:mysql:database=test;mysql2.st ern.nyu.edu;port=3306", user, pass); my $sth = $dbh->prepare($query); $sth->execute; my $sth = $dbh->prepare($query); $sth->execute;

12. M.P. Johnson, DBMS, Stern/NYU, Sp2004 12 Perl DBI 3. Extract next row of data from statement results, if available:  What this means: row has two fields, whose values are put in $a and $b, in order  Other options, but this should suffice In general, want to scroll through results:  Braces { } are required! my ($a, $b) = $sth->fetchrow_array() while (my ($a, $b) = $sth->fetchrow_array()) { # print out $a and $b } while (my ($a, $b) = $sth->fetchrow_array()) { # print out $a and $b }

13. M.P. Johnson, DBMS, Stern/NYU, Sp2004 13 Limit: Perl webpages that do something Semi-interesting Perl script:  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/lookup.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/lookup.cgi Non-trivial but not huge: ~40 lines Works with two-column (a,b) table  Takes input from user  Returns rows whose a field contains value  If no/empty input, returns all rows Bad idea in general!

14. M.P. Johnson, DBMS, Stern/NYU, Sp2004 14 lookup.cgi Two possible situations for running script: 1. Page opened for the first time 2. User entered parameter and pressed button Structure of file: 1. Print input box and button for next search  On button click, parameter is sent to this page’s url 2. (Try to) read input parameter 3. Open MySQL connection 4. Run query 5. Print results in a table 6. Disconnect from MySQL

15. M.P. Johnson, DBMS, Stern/NYU, Sp2004 15 Higher-level structure As one page:  If we have params, display data based on them  Otherwise, prompt user for params, call self Could be:  Page 1: prompt for params, call page 2  Page 2: display data based on params In e.g.: always display data for convenience

16. M.P. Johnson, DBMS, Stern/NYU, Sp2004 16 Tutorials on Perl Some material drawn from the following good tutorials: http://perl.com CGI backend programming using perl:  http://www.scit.wlv.ac.uk/~jphb/sst/perl/ http://www.scit.wlv.ac.uk/~jphb/sst/perl/ Perl Basics:  http://www.cs.wcupa.edu/~rkline/csc417/perl-basics-1.html http://www.cs.wcupa.edu/~rkline/csc417/perl-basics-1.html CGI Basics:  http://www.cs.wcupa.edu/~rkline/csc417/cgi-basics-1.html http://www.cs.wcupa.edu/~rkline/csc417/cgi-basics-1.html MySQL/Perl/CGI example:  http://www.scit.wlv.ac.uk/~jphb/sst/perl/ex3d.html http://www.scit.wlv.ac.uk/~jphb/sst/perl/ex3d.html

17. M.P. Johnson, DBMS, Stern/NYU, Sp2004 17 That’s all, folks! Q: Is this enough to get a job coding Perl? A: Probably not! But: Don’t like Perl/CGI? Don’t want to run start a process for every user of your site? Next we’ll do PHP… a couple modified copies of lookup.cgi and cia.cgi + some HTML  fairly interesting site a couple modified copies of lookup.cgi and cia.cgi + some HTML  fairly interesting site

18. M.P. Johnson, DBMS, Stern/NYU, Sp2004 18 Dynamic webpages Original prob: need webpages to respond to user inputs Soln 2:  create a an html file embedded with special non- html code  upon url request, execute embedded code to generate more html  Send back the modified html page to user  An incomplete html page exists on server  PHP, JSPs, ASPs, etc.

19. M.P. Johnson, DBMS, Stern/NYU, Sp2004 19 New topic: PHP First option: for each request: run program, produce whole page, send back  CGI and some host language Second option: create html page with missing parts; for each response, fill in the wholes and send back  Embedded scripting  PHP and others  PHP = Personal Home Page or = PHP Hypertext Processor

20. M.P. Johnson, DBMS, Stern/NYU, Sp2004 20 hello.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/hello.php Q: What the difference between and \n? Hello from PHP Here is the PHP part: \n“; ?> That's it! Hello from PHP Here is the PHP part: \n“; ?> That's it!

21. M.P. Johnson, DBMS, Stern/NYU, Sp2004 21 hello2.php Script errors, w/ and w/o display_errors on:  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello2.php http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello2.php  http://pages.stern.nyu.edu/~mjohnson/dbms/php/hello2.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/hello2.php Local dir must contain.htaccess:  Automatically load GET/POST params as vars  http://pages.stern.nyu.edu/~mjohnson/dbms/php/.htaccess http://pages.stern.nyu.edu/~mjohnson/dbms/php/.htaccess php_flag display_errors on php_flag register_globals on php_flag display_errors on php_flag register_globals on

22. M.P. Johnson, DBMS, Stern/NYU, Sp2004 22 More on PHP Somewhat C-like, somewhat Perl-like Case-sensitive Comments:  # Unix shell-style  /* */ C-style  // C++-style Output:  echo(“hi there”);  C’s printf

23. M.P. Johnson, DBMS, Stern/NYU, Sp2004 23 PHP vars Similar to those of Perl  http://pages.stern.nyu.edu/~mjohnson/dbms/php/math.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/math.php <? $num1 = 58; $num2 = 67; print "First number ". $num1. " "; print "Second number ". $num2. " "; $total = $num1 + $num2; print "The sum is ". $total. " "; ?> <? $num1 = 58; $num2 = 67; print "First number ". $num1. " "; print "Second number ". $num2. " "; $total = $num1 + $num2; print "The sum is ". $total. " "; ?>

24. M.P. Johnson, DBMS, Stern/NYU, Sp2004 24 Combining PHP and HTML http://pages.stern.nyu.edu/~mjohnson/dbms/php/combine.php <?php for($z=0;$z<=5;$z++) { ?> Iteration number <? } ?> <?php for($z=0;$z<=5;$z++) { ?> Iteration number <? } ?>

25. M.P. Johnson, DBMS, Stern/NYU, Sp2004 25 PHP info PHP does not have both string and number ops like Perl Number ops treat (number) strings as numbers, regular strings as strings  http://pages.stern.nyu.edu/~mjohnson/dbms/php/test.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/test.php Info function displays lots of PHP/HTML info:  http://pages.stern.nyu.edu/~mjohnson/dbms/php/info.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/info.php

26. M.P. Johnson, DBMS, Stern/NYU, Sp2004 26 PHP & MySQL 1. Open a connection and open our DB: 2. Run query: $db = mysql_connect("mysql2.stern.nyu.edu:3306", user, pass); mysql_select_db("test", $db); $db = mysql_connect("mysql2.stern.nyu.edu:3306", user, pass); mysql_select_db("test", $db); $result = mysql_query($query,$db);

27. M.P. Johnson, DBMS, Stern/NYU, Sp2004 27 PHP & MySQL 3. Extract next row of data from statement, if available:  What this means: myrow is an array that can then be accessed  Other options, but this should suffice In general, want to scroll through results: $myrow = mysql_fetch_row($result) while ($myrow = mysql_fetch_row($result)) # print row’s data while ($myrow = mysql_fetch_row($result)) # print row’s data

28. M.P. Johnson, DBMS, Stern/NYU, Sp2004 28 Limit: PHP webpages that do something Semi-interesting Perl script:  http://pages.stern.nyu.edu/~mjohnson/dbms/php/lookup.php http://pages.stern.nyu.edu/~mjohnson/dbms/php/lookup.php  Non-trivial but not huge: ~60 lines, but much plain html Works with two-column (a,b) table Takes input from user Returns rows whose a field contains value If no/empty input, returns all rows  Bad idea in general!

29. M.P. Johnson, DBMS, Stern/NYU, Sp2004 29 lookup.php: port of lookup.cgi Two possible situations for running script: 1. Page opened for the first time 2. User entered parameter and pressed button Structure of file: 1. Print input box and button for next search  On button click, parameter is sent to this page’s url 2. (Try to) read input parameter 3. Open MySQL connection 4. Run query 5. Print results in a table 6. Disconnect from MySQL

30. M.P. Johnson, DBMS, Stern/NYU, Sp2004 30 Insert/delete Perl/PHP example Similar to search example NB: form has two buttons http://pages.stern.nyu.edu/~mjohnson/dbms/perl/update.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/updatecgi.txt http://pages.stern.nyu.edu/~mjohnson/dbms/perl/update.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/php/updatephp.tx t http://pages.stern.nyu.edu/~mjohnson/dbms/php/updatephp.tx t

31. M.P. Johnson, DBMS, Stern/NYU, Sp2004 31 Master-detail Perl/PHP example Idea: display list of regions;  When region clicked on, display its countries Mechanism: pass GET param in link, not with a FORM http://pages.stern.nyu.edu/~mjohnson/websy s/cia.pl http://pages.stern.nyu.edu/~mjohnson/websy s/cia.pl http://pages.stern.nyu.edu/~mjohnson/websy s/cia.php.txt http://pages.stern.nyu.edu/~mjohnson/websy s/cia.php.txt

32. M.P. Johnson, DBMS, Stern/NYU, Sp2004 32 Tutorials on PHP Some material drawn from the following good tutorials: http://php.net PHP introduction and examples:  http://www.scit.wlv.ac.uk/~jphb/sst/php/ http://www.scit.wlv.ac.uk/~jphb/sst/php/ Interactive PHP with database access:  http://www.scit.wlv.ac.uk/~jphb/sst/php/gazdb.html http://www.scit.wlv.ac.uk/~jphb/sst/php/gazdb.html Longer PHP/MySQL Tutorial from webmonkey:  http://hotwired.lycos.com/webmonkey/99/21/index2a.html http://hotwired.lycos.com/webmonkey/99/21/index2a.html Nice insert/update/delete example from webmonkey:  http://hotwired.lycos.com/webmonkey/99/21/index3a.html http://hotwired.lycos.com/webmonkey/99/21/index3a.html MySQL/Perl/PHP page from U-Wash:  http://www.washington.edu/computing/web/publishing/mysql-script.html http://www.washington.edu/computing/web/publishing/mysql-script.html

33. M.P. Johnson, DBMS, Stern/NYU, Sp2004 33 Comparison of scripting languages PHP v. Perl:  http://php.weblogs.com/php_versus_perl http://php.weblogs.com/php_versus_perl PHP v. Perl v. Java servlets v. …:  http://www.developerspot.com/tutorials/php/server -side-scripting-language/ http://www.developerspot.com/tutorials/php/server -side-scripting-language/

34. M.P. Johnson, DBMS, Stern/NYU, Sp2004 34 Advice for use of novel languages 1. Rerun often  don’t wait until end to try 2. Use frequent prints to be sure of var vals 3. When stuck, picture continuum from your current program to some other program  other prog. works but doesn’t do what you want  change either/both, step by step, until they meet in the middle

35. M.P. Johnson, DBMS, Stern/NYU, Sp2004 35 That’s really all, folks! Q: Is this enough to get a job coding PHP? A: Again, probably not. But: again pretty easy to produce a semi-interested site with a few copies of lookup.php and cia.php. Don’t like PHP either? Lots of other choices, but again, you’re strongly discouraged from using something else for your project unless you know what you’re doing.