PHP

Outline  What is PHP?  What can PHP do?  PHP Basics  PHP and Forms  Cookies and Sessions  Database Connections  Command Line PHP  Other PHP capabilities  Useful Links Slide # 2

What is PHP??  PHP: Hypertext Preprocessor  PHP is a scripting language that allows you to create dynamic web pages  You can embed PHP scripting within normal html coding  PHP was designed primarily for the web  PHP includes a comprehensive set of database access functions Slide # 3

What can PHP do?  Server side scripting CGI Server module  Command line scripting  GUI applications  Some of the protocols PHP speaks: LDAP, IMAP, SNMP, NNTP, POP3, HTTP, CORBA, XML(SAX/DOM), Perl regular expressions, Cybercash payment, CyberMUT, VeriSign Payflow Pro, and most relational databases Slide # 4

PHP Basics PHP echos everything to standard output until it comes across special tags:,, <? if ($expression) { ?> This is true. <? } else { ?> This is false. <? } ?> Slide # 5

PHP Basics (contd.)  Comments:  // /* */ #  Variable Types  boolean $foo = True;  integer $a=1234; $a=0123; $a=0x1A;  float $a=1.234; $a=1.2e3; $a=7E-10;  string $name = 'MyName';  array $arr[key] = value;  object  Variables  All variables begin with $ and can contain letters,  digits and underscore (and no digit directly after the $)  The value of a variable is the value of its most recent assignment  Don’t need to declare variables  Variables have no intrinsic type other than the type of their current value  Can have variable variables $$variable  Like a pointer variable type; best to avoid Slide # 6

Predefined Variables  $GLOBALS  $_SERVER  $_GET  $_POST  $_COOKIE  $_FILE  $_REQUEST  $_SESSION Slide # 7

Variable scope  The scope of a variable is the context within which it is defined.  Within user-defined functions a local function scope is introduced. Any variable used inside a function is by default limited to the local function scope.  This is circumvented by using the “global” or “static” declaration: function Sum() { global $a, $b; $b = $a + $b; } Slide # 8

Control Strctures  if  else  elseif  while  do..while  for  foreach  break  continue  switch  declare  return  require()  include()  require_once()  include_once() Slide # 9

Functions Default argument values  function foo ($arg_1="value", $arg_2=7.3,..., $arg_n) Variable-length argument lists  func_num_args()  func_get_arg() function foo ($arg_1, $arg_2,..., $arg_n) { echo "Example function.\n"; return $retval; } function square ($num) { return $num * $num; } echo square (4); // outputs '16' Slide # 10

Objects Slide # 11 <?php class Cart { var $items; // Items in our shopping cart function Cart() { $this->todays_date = date("Y-m-d"); $this->name = $GLOBALS['firstname']; /* etc... */ } // Add $num articles of $artnr to the cart function add_item ($artnr, $num) { $this->items[$artnr] += $num; } // Take $num articles of $artnr out of the cart function remove_item ($artnr, $num) { if ($this->items[$artnr] > $num) { $this->items[$artnr] -= $num; return true; } else { return false; } ?>

PHP and Forms Slide # 12 An example HTML form: Name: Username: Beer: Warthog Guinness Stuttgarter

PHP and Forms (contd.) Variables accessible in array.php:  $_POST[“personal”][“name”]  $_POST[“personal”][“ ”]  $_POST[“beer”]  $_POST[“username”] For more on HTML forms: Slide # 13

PHP and Forms (contd.) Passing variables from page to page: $username from array.php will be available for array2.php Array.php: ” Favorite Color: Slide # 14

A form processing example <? while($temp = each($_POST)) { echo "Variable $temp[‘key’] contains ” echo “ $temp[‘value’] "; } ?> Slide # 15

GET vs. POST  GET  Accessed through the $_GET variable  Puts variables in the URL  Doesn’t require user to click “reload” if they revisit a page with the “back” button  Good for passing small amounts of data  POST  Accessed through the $_POST variable  Passes variables in Content HTTP directive … not in URL  If a user clicks the “back” button, the browser will ask the user to reload the page  Good for passing large amounts of data, but may cause navigation problems Slide # 16

Cookies Cookies are useful for storing user info that should be retained from one page to the next. (Overcome the ‘stateless’ nature of the web) Cookies are written to the client’s hard drive. Problems:  User can disable cookies in the browser  Cookies may be viewed by other users  Can only store 20 cookies; max 4KB.  Some browsers may display incorrectly unless all options are set in setcookie() Slide # 17

Creating a Cookie setcookie(name,value,expiration); Eg, setcookie(“fruit”,”banana”,time()+3600); The cookies is called ‘fruit’ and has a value of ‘banana’; it will expire 1 hr from now. Cookie values are sent as part of the HTTP headers (transparent to user). No output should be sent to the browser (echo etc) until the cookie is set else cookie will not be set. Slide # 18

Cookie (contd.) Accessing A Cookie  $_COOKIE contains the value of every current cookie <? foreach ($_COOKIE as $name =>$value) echo “ $name => $value”; ?> Deleting a Cookie  Automatically deleted after expiration time  You can manually delete by setting negative time  setcookie(“username”,””,time()-3600); Slide # 19

Redirection Once login data is captured/validated then want to go to a new page.  Header(“Location: URL”); header("Location: General technique:  Site start page = login page  Login page validates user and set cookies  Redirect to new page  New page uses cookie data to access DB info Slide # 20

Sessions  Used to store state across pages  To save a variable simply set it in the $_SESSION variable:  $_SESSION[“username”] = $username;  To access a saved variable, access the $_SESSION variable:  $username = $_SESSION[“username”];  To remove a variable, unset the $_SESSION variable:  unset($_SESSION[“username”]);  Slide # 21

Databases and PHP  PHP can access many types of RDBMS’s MySQL, M$SQL, Oracle, Sybase, M$ Access, dBase, dbm, PostgreSQL  Use database independent interfaces  My inc.db.php script  DB.php in PEAR   ADODB  Slide # 22

Command Line PHP  What is this good for:  Parsing files to put into a database  Updating files with latest public version (cron job)  Anything you’d use a shell script or perl script to do!  Variables of use:  $argc, $argv[]  $stdin, $stdout, $stderr Slide # 23

Other PHP capabilities  IMAP  XML parsing  FTP  IRC  Java  LDAP  Mail  Ncurses  OpenSSL  Regular Expressions  Compression  PDF file generation  Shockwave Flash  COM and.NET objects  Password strength tests  CURL  Ecommerce protocols Slide # 24

Useful Links  PHP main site:   Zend’s PHP Intro:   PHPBuilder:  Slide # 25

Slide # 26 Thank You