Dynamic Web Sites with PHP

1
Dynamic Web Sites with PHP MySQL

• Introduction - Features
• Syntax with examples
• Database handling with example
• Useful hints
• How to get help

2
Introduction

• PHP is a tool that lets you create dynamic web
  pages
• PHP-enabled web pages are treated just like
  regular HTML pages and you can create and edit
  them the same way you normally create regular
  HTML pages
• PHP stands for 'Hypertext Pre-Processor'
• PHP is script embedded in HTML file, which can
  generate dynamic HTML contents
• It is a server side HTML object-oriented
  scripting/programming language
• Client transparent

3
What is PHP?

• At the most basic level, PHP can do anything any
  other CGI program can do, such as
• collect form data
• generate dynamic page content, or
• send and receive cookies
• PHP also has support for talking to other
  services using protocols such as
• IMAP
• SNMP
• NNTP
• POP3
• HTTP
• PHP can also
• open network sockets and
• interact using other protocols

4
Functions Features

• Built in support for
• Email, FTP, XML, PDF
• Extensive database support
• Fully support to all data base products
• Over 1000 functions and 50 Modules!
• HTTP authentication with PHP
• GIF creation with PHP - GD library
• File upload support
• HTTP cookie support
• Error connection handling
• PHP source viewer
• Provide easy and powerful hypertext manipulation
• High performance ( 400,000 visitors per day)

5
History of PHP (Part 1)

• PHP is a powerful server side web scripting
  solution
• 1994 Personal project of Rasmus Lerdorf
• He combined his Personal Home Page tools scripts
  with the Form Interpreter, added mSQL support,
  which resulted the PHP/FI
• PHP/FI grew at an amazing pace and people started
  contributing code to it
• By late 1996 PHP/FI was in use on at least 15,000
  web sites around the world
• By mid-1997 this number had grown to over 50,000
• 1997 New parser (PHP 3.0) from Zeev Suraski
  Andi Gutmans
• In the PHP 4 the parser is the Zend Engine

6
History of PHP (Part 2)

• It has quickly grown in popularity and according
  to the February 2001 usage stats PHP is
  installed on 19.8 of all web sites
• in 2000 it was 7, only
• The goal of the language is to allow web
  developers to write dynamically generated pages
  quickly
• CGI is more powerful in general, while PHP is
  more convenience to use and write
• A lot of possibility of joining to the PHP
  community...

7
Grow of PHP Usage I
8
Grow of PHP Usage II
9
Why use PHP?

• Today Version 4 powerful language
• Cross-platform, extensible, FAST
• Very easy to learn / teach
• Cheap
• Great online community support
• It had become the most well-known and most widely
  used scripting language for
• Web, Internet, e-commerce, business-to-business
  projects
• Speed
• PHP runs 5 to 20 times faster than Java
• It is extremely easy to use and you can develop
  very complex web/e-commerce applications very
  rapidly in a very short period of time

10
Database Support

• The strongest and most significant feature in PHP
  is its support for a wide range of databases
• Writing a database-enabled web page is incredibly
  simple
• The following databases are currently supported
  
• Adabas D Ingres Oracle
• dBase InterBase Ovrimos Informix
• Empress FrontBase PostgreSQL ODBC
• FilePro mSQL Direct MS-SQL dbm
• Solid Hyperwave Sybase IBM DB2
• MySQL Velocis Unix dbm

11
Platforms

• The power of PHP is that it is cross-platform and
  runs everywhere
• It runs on many web-servers like
• Apache (built-in)
• Microsoft IIS, others (as CGI binary)
• It runs on
• Linux
• Windows 95/98/NT
• Windows 2000
• Solaris
• HPUX and
• all flavors of Unix
• PHP is write once and deploy anywhere and
  everywhere

12
What do I need?

• The server has to have support for PHP activated
  and that all files ending in .php3 are handled by
  PHP
• On most servers this is the default extension for
  PHP files, but ask your server administrator to
  be sure
• If your server supports PHP then you don't need
  to do anything
• Just create your .php3 files and put them in your
  web directory and the server will magically parse
  them for you
• There is no need to compile anything nor do you
  need to install any extra tools
• Think of these PHP-enabled files as simple HTML
  files with a whole new family of magical tags
  that let you do all sorts of things

13
The Configuration File

• The configuration file (called php.ini) is read
  when PHP starts up
• For the server module versions of PHP, this
  happens only once when the web server is started
• For the CGI version, it happens on every
  invocation
• When using PHP as an Apache module, you can also
  change the configuration settings using
  directives in Apache configuration files and
  .htaccess files
• You can view the settings of the configuration
  values in the output of phpinfo()

14
Syntax

• Much of its syntax is borrowed from C, Java and
  Perl with some unique PHP-specific features
  thrown in
• Control structures
• if, else, for, do while, switch etc
• Types
• Integers, strings, arrays, objects
• Classes (OOP) and Functions
• Syntax of PHP is similar to the basic syntax used
  by the C language
• All the string and memory manipulation issues in
  C have been eliminated in PHP, but the basic
  syntax remains
• PHP can be compiled and optimized to make it run
  even faster by using the Zend Optimizer
• Zend optimizer is integrated with PHP in PHP
  version 4.0

15
Instruction Separation

• Instructions are separated the same as in C or
  perl - terminate each statement with a semicolon
• The closing tag (?gt) also implies the end of the
  statement, so the following are equivalent
• lt?php
• echo "This is a test"
• ?gt
• lt?php echo "This is a test" ?gt

16
Hello World Example I

• lthtmlgt
• ltheadgt
• lttitlegtPHP Example Ilt/titlegt
• lt/headgt
• ltbodygt
• lt?php
• print Hello World!"
• ?gt
• lt/bodygt
• lt/htmlgt

17
Another Hello World Example I

• Create a file named hello.php3 and in it put the
  following lines
• lthtmlgt
• ltheadgt
• lttitlegtPHP Example IIlt/titlegt
• lt/headgt
• ltbodygt
• lt?php echo "Hello WorldltPgt" ?gt
• lt/bodygt
• lt/htmlgt
• The file does not need to be executable or
  special in any way
• Think of it as a normal HTML file which happens
  to have a set of special tags available to you
  that do a lot of interesting things

18
Another Hello World Example II

• This program is extremely simple and you really
  didn't need to use PHP to create a page like this
• All it does is display
• Hello World
• If it didn't output anything, chances are that
  the server you are on does not have PHP enabled
• Ask your administrator to enable it for you
• The point of the example is to show the special
  PHP tag format
• In this example lt?php was used to indicate the
  start of a PHP tag
• Then the PHP statement and left PHP mode was put
  by adding the closing tag, ?gt
• You may jump in and out of PHP mode in an HTML
  file like this all you want

19
Architecture of a PHP-based DBM Application
20
First Steps in the MySQL Usage

• Let the name of the database is mydata_dbuse
  mydata_dbcreate table student (name
  VARCHAR(30), supervisor VARCHAR(30), birthdate
  DATE)insert into student (name, supervisor,
  birthdate) values ("John Little","Andreas Big",
  "1979-10-20")insert into student (name,
  supervisor, birthdate) values ("Erica
  Knight","Andreas Big", "1980-11-22")select
  from student where supervisor like "Big"update
  student set supervisor "Edward Teller" where
  name"Erica Knight"commitquit
• The home page of the mysql documentationhttp//w
  ww.mysql.com/documentation/mysql/bychapter/index.h
  tml

21
Checking the User Agent

• E.g. we are going to check what sort of browser
  the person viewing the page is using
• In order to do that we check the user agent
  string that the browser sends as part of its
  request
• This information is stored in a variable
• Variables always start with a dollar-sign in PHP
• The variable we are interested in is
  HTTP_USER_AGENT
• To display this variable we can simply do
• lt?php echo HTTP_USER_AGENT ?gt
• For the browser that you are using right now to
  view this page, this displays
• Mozilla/4.0 (compatible MSIE 5.0 Windows
  98 DigExt)

22
Function Names

• They are case insensitive
• Even all of the built in PHP functions are case
  insensitive
• function foo ()
• return 'foo'
• function FOO ()
• return 'FOO'
• // error function foo() already declared

23
Variables

• Variables are case sensitive
• foo 'foo'
• FOO 'FOO'
• echo "fooFOO"
• // prints fooFOO

24
Other Variables

• There are many other variables that are
  automatically set by your web server
• You can get a complete list of them by creating a
  file that looks like this
• lt?php phpinfo()?gt
• Then load up this file in your browser and you
  will see a page full of information about PHP
  along with a list of all the variables available
  to you

25
Usage of the Variables

• In PHP, a variable does not require formal
  declaration
• It will automatically be declared when a value is
  assigned to it
• Variables are prefixed by a dollar sign
  (VariableName)
• In the following example, four variables are
  automatically declared by assigning a value to
  them
• lt?php
• number 5
• string1 "this is a string\n"
• string2 'this is another "string"'
• real 37.2
• ?gt

26
Variables

• Variables that have not been set are defined as
  NULL
• If you use a variable that has not been set then
  PHP will treat the NULL like it is an empty
  string
• But, don't depend on your variables being empty
  unless you have explicitly set them to be so
• Users can pass arbitrary variable values into
  your script using the GET and POST HTTP methods

27
Types

• For the most part, types are hidden from the
  developer in PHP
• 99 of the time you don't know or care about the
  type of a variable since PHP is so good at doing
  automatic conversions
• There are times however when the type of your
  variables does become important

28
Types of the PHP4

• array
• boolean
• double
• integer
• null
• variables that are not set
• object
• resource
• variables that represent resources such as file
  or database handles
• string
• unknown type

29
Converting Types

• PHP4 has introduced a concept of identity to the
  language
• Two values are identical if they have the same
  content and the same type
• Equality is based on two values having the same
  content after they have been converted to the
  same type
• Equality () of two variables is not the same as
  identity ()
• You can explicitly cast and convert between types
  in PHP when necessary
• The main time you need to think about doing this
  is when you are trying to do comparisons between
  variables of unknown or different types

30
Example of Types

• A good example of where types can get tricky is
  with database operations
• Any return value from a database will always be
  represented in PHP as a string
• The type in the database is irrelevant,
  immediately upon its return to PHP the value will
  be a string
• Implicit conversion will treat this string as an
  integer, but it is still a string
• There is one notable exception however
• If you get a NULL return value from the database
  then PHP will create a variable of type NULL
• ie. effectively the variable is not set

31
References

• All variable assignments in PHP are done by
  copying values
• Every time you assign a value to a variable you
  are creating a copy
• Most of the time this doesn't really matter and
  in fact protects programmers from themselves
  since they can't destroy their precious data
• Sometimes however copying by value can be a
  burden if your data is large and the copy isn't
  really necessary
• To get around this problem PHP lets you create
  references to data
• E.g., you can make b reference the same data as
  a with this command
• b a

32
Arrays I

• PHP arrays are a cross between numbered arrays
  and associative arrays
• This means that you can use the same syntax and
  functions to deal with either type of array,
  including arrays that are
• Indexed from 0
• Indexed by strings
• Indexed with non-continuous numbers
• Indexed by a mix of numbers and strings
• In the next example, three literal arrays are
  declared as follows
• 1.A numerically indexed array with indices
  running from 0 to 4
• 2.An associative array with string indices
• 3.A numerically indexed array, with indices
  running from 5 to 7

33
Arrays II

• lt?php
• array1 array(2, 3, 5, 7, 11)
• array2 array("one" gt 1, "two" gt 2, "three"
  gt 3)
• array3 array(5 gt "five", "six", "seven")
• printf("7 d, 1 d, 'six' s\n", array13,
  array2"one", array36)
• ?gt
• From the above example, the indices in the array1
  are implicit, while the indices in array2 are
  explicit
• When specifically setting the index to a number N
  with the gt operator, the next value has the
  index N1 by default
• Explicit indices do not have to be listed in
  sequential order
• You can also mix numerical and string indexes,
  but it is not recommended

34
Conditionals and Looping Constructs I

• PHP includes if and elseif conditionals, as well
  as while and for loops, all with syntax similar
  to C
• The example below introduces these four
  constructs
• lt?php
• // Conditionals
• if (a)
• print "a is trueltBRgt\n"
• elseif (b)
• print "b is trueltBRgt\n"
• else
• print "neither a or b is trueltBRgt\n"

35
Conditionals and Looping Constructs II

• // Loops
• do
• c test_something()
• while (c)
• while (d)
• print "okltBRgt\n"
• d test_something()
• for (i 0 i lt 10 i)
• print "iiltBRgt\n"
• ?gt

36
Architecture FOR Loop

• Build-in module in Apache web server
• Example

Apache httpd
request
PHP module Proxy module GIF module DB module
html
lthtmlgtltbodygt lt?php for(t1tlt5t)
echo "ltpgthello ".t."times" ?gt lt/bodygtlt/htmlgt
hello 1 times hello 2 times hello 3 times hello 4
times hello 5 times
37
Usage of Functions I

• PHP parses one file at a time
• Thus, you can use any function that has already
  been declared or is declared as part of the
  current file
• So, this is valid
• foo()
• function foo ()
• echo 'foo'

38
Usage of Functions II

• If we move the foo() function into an include
  file the above ordering will no longer work
  regardless of whether we use include() or
  require() since PHP will attempt to run that step
  after the call to the function foo()
• So, this will not work
• foo()
• include('./foo.inc')

39
If Statement

• You can put
• multiple PHP statements inside a PHP tag
• create little blocks of code (that do more than
  just a single echo)
• E.g., if we wanted to check for Internet Explorer
  we could do something like this
• lt?php if(strstr(HTTP_USER_AGENT,"MSIE"))
• echo "You are using Internet
  Explorerltbrgt"
• ?gt

40
The strstr() Funcion Call I

• strstr() is a function built into PHP which
  searches a string for another string
• In this case we are looking for "MSIE" inside
  HTTP_USER_AGENT
• If the string is found the function returns true
  and if it isn't, it returns false
• If it returns true the following statement is
  executed

41
The strstr() Funcion Call II

• We can take this a step further and show how you
  can jump in and out of PHP mode even in the
  middle of a PHP block
• lt?php
• if(strstr(HTTP_USER_AGENT,"MSIE"))
• ?gt
• ltCENTERgtltBgtYou are using Internet
  Explorerlt/Bgtlt/CENTERgt
• lt?
• else
• ?gt
• ltCENTERgtltBgtYou are not using Internet
  Explorerlt/Bgtlt/CENTERgt
• lt?
• ?gt

42
The strstr() Funcion Call III

• Instead of using a PHP echo statement to output
  something, we jumped out of PHP mode and just
  sent straight HTML
• The important and powerful point to note here is
  that the logical flow of the script remain intact
• Only one of the HTML blocks will end up getting
  sent to the viewer
• Running this script right now results in
• You are using Internet Explorer

43
Dealing with Forms

• One of the most powerful features of PHP is the
  way it handles HTML forms
• The basic concept that is important to understand
  is thatany form element in a form will
  automatically result in a variable with the same
  name as the element being created on the target
  page
• By default, any form entry creates a global PHP
  variable of the same name
• One of PHP's oldest features is the ability to
  make HTML form and cookie data available directly
  to the programmer

44
Web Application Features

• In the followings, a user name is retrieved and
  assigned to a variable
• The name is then printed by the sub-routine
  "submit.php"
• ltFORM METHOD"GET" ACTION"submit.php"gt
• What's your name?
• ltINPUT NAME"myname" SIZE3gt
• lt/FORMgt
• submit.php
• lt?php
• print "Hello, myname!"
• ?gt
• From the above example, note that variables can
  also be referenced from within double quoted
  strings

45
Simple Example for Forms

• Assume you have a page with a form like this on
  it
• ltFORM ACTION"action.php3" METHOD"POST"gt
• Your name ltINPUT TYPEtext NAMEnamegt
• You age ltINPUT TYPEtext NAMEagegt
• ltINPUT TYPEsubmitgt
• lt/FORMgt
• There is nothing special about this form
• It is a straight HTML form with no special tags
  of any kind
• When the user fills in this form and hits the
  submit button, the action.php3 page is called
• In this file you would have something like this
• Hi lt?php echo name?gt. You are lt?php echo
  age?gt years old
• It should be obvious what this does
• The name and age variables are automatically
  set for you by PHP

46
Debugging

• The classic debugging technique for PHP (and many
  other languages) is through echo statements
• Just dump out information or the contents of your
  variables at various points in the script
• There are some tricks that you can use to make
  debugging more effective
• log messages to file rather than printing so you
  don't affect HTTP headers
• your HTML output use print_r or var_dump to
  examine the contents of any variable
• There are some PHP debuggers coming onto the
  market that allow you to step through PHP code
  line by line

47
Comments

• PHP supports 'C', 'C' and Unix shell-style
  comments
• E.g.
• lt?php
• echo "This is a test" // This is 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
• ?gt

48
Usage of Comments

• The "one-line" comment styles actually only
  comment to the end of the line or the current
  block of PHP code, whichever comes first
• lth1gtThis is an lt? echo "simple"?gt example.lt/h1gt
• ltpgtThe header above will say 'This is an
  example'.
• You should be careful not to nest 'C' style
  comments, which can happen when commenting out
  large blocks
• lt?php
• /
• echo "This is a test" / This comment will
  cause a problem /
• /
• ?gt

49
Built-in Variables

• PHP has a number of built-in variables that give
  you access to your Web server's CGI environment,
  form/cookie data and PHP internals. Here are some
  of the most useful variables
• PHP internal variables
• The GLOBALS and PHP_SELF variables shown in the
  table below are specific to PHP
• Variable Name Description
  
• GLOBALS An associative array of all global
  variables
• You can access it anywhere without declaring
  it
• as a global first
• PHP_SELF This is the current script

50
HTTP Request Variables

• HTTP request variables are derived from their
  corresponding HTTP headers
• E.g., HTTP_USER_AGENT is derived from the
  User-Agent header, presented in the table below
• HTTP_HOST
• Host name in the browser's "location" field
• HTTP_USER_AGENT
• User agent (browser) being used
• HTTP_REFERER
• URL of the referring page

51
Database Handling

• Communication with MySQL
• PHP and MySQL are often referred to as the
  "dynamic duo" of dynamic Web scripting
• PHP and MySQL work very well together, in
  addition to the speed and features of each
  individual tool
• The following is a simple example of how to dump
  the contents of a MySQL table using PHP
• The example assumes you have a MySQL user called
  "nobody" who can connect with an empty password
  from localhost
• In this example, PHP implements the following
  procedure
• Connect to MySQL
• Send a query
• Print a table heading
• Print table rows until end of the table has been
  reached

52
MySQL Example I

• lt?php
• //Connect to the database on the server's machine
  as
• //user "Nobody".
• conn mysql_connect("localhost", "nobody", "")
  
• res mysql_query("SELECT FROM mytable",
  conn)
• header_printed false
• print "ltTABLEgt\n"
• do
• data mysql_fetch_array(res)
• // Retrieve the next row of data.
• if (!is_array(data))
• break

53
MySQL Example II

• // This part is done only on the first loop. It
  prints
• // out the names of the fields as table headings.
  This
• // ensures that the headings will only be printed
  if the
• // database returns at least one row
• if (!header_printed)
• print " ltTRgt"
• reset(data)
• while (list(name, value) each(data))
• print " ltTHgtnamelt/THgt\n"
• print " lt/TRgt\n"
• header_printed true
• print " ltTRgt\n"
• print " ltTDgt"

54
MySQL Example III

• // Instead of looping through the returned data
  fields,
• // we use implode to create a string of all data
  items
• // with the required HTML between them.
• print implode("lt/TDgt\n ltTDgt", data)
• print " lt/TRgt\n"
• while (data)
• print "lt/TABLEgt\n"
• ?gt

55
Communication with Other Databases

• Unlike other scripting languages for Web page
  development, PHP is
• open-source
• cross-platform, and
• offers excellent connectivity to most of today's
  common databases including
• Oracle
• Sybase
• MySQL
• ODBC (and others)
• PHP also offers integration with various external
  libraries which enable the developer to do
  anything
• from generating PDF documents to parsing XML

56
Code Reusage

• Use existing code when it is available, just
  integrate it into your standards and project
• Develop a library of helpful functions
• A good advice Web gurus know that speed of
  coding is much more important than speed of code
• PHP was born and raised in an open source
  environment
• The community holds open source ideals close to
  its heart
• As a result there are thousands of people on the
  mailing list willing to share their knowledge and
  code
• PHP has a huge user base and a large developer
  base as it runs on both Window95/NT and all
  flavors of Unixes
• Not suggested to spend all day asking people to
  write code for you
• But through clever use of resources (next
  slide), mailing list archives and PHP projects
  you can save yourself a lot of time

57
Useful Codes

• There are a number of useful code modules you can
  use
• PHP Resources
• PHP Code Exchange
• PHP Classes Repository
• PHP Knowledge Base
• PHP Mailing List Archive
• Address (e.g.)
• http//www.e-gineer.com/clickthrough/
• They include things like
• database abstraction layer
• session management
• debugging libraries
• logging functions
• timing code

58
Problems FAQ Bug Reports

• Read the FAQ
• Some problems are more common than others
• The most common ones are listed in the PHP FAQ,
  found at
• http//www.php.net/FAQ.php3
• Bug reports
• If you think you have found a bug in PHP, please
  report it
• The PHP developers probably don't know about it,
  and unless you report it, chances are it won't be
  fixed
• You can report bugs using the bug-tracking system
  at
• http//www.php.net/bugs.php3

59
Archives Downloadingthe Latest Version

• If you are still stuck, someone on the PHP
  mailing list may be able to help you
• You should check out the archive first, in case
  someone already answered someone else who had the
  same problem as you
• The archives are available from the support page
  on
• http//www.php.net/
• The source code, and binary distributions for
  some platforms (including Windows), can be found
  at
• http//www.php.net/

60
Mailing list for Discussing the Problems

• To subscribe to the PHP mailing list, send an
  empty mail to
• php3-subscribe_at_lists.php.net
• The mailing list address is
• php3_at_lists.php.net
• If you want to get help on the mailing list,
  please
• try to be precise and give the necessary details
  about your environment
• which operating system
• what PHP version
• what web server if you are running PHP as CGI or
  a server module, etc.
• and preferably enough code to make others able to
  reproduce and test your problem