IMTA 99

1
PHP Hypertext Preprocessor
Ilker BEKMEZCI
Advanced Network Programming Bogaziçi University,
Fall 2000
PHP
2
Introduction

• PHP, which stands for "PHP Hypertext
  Preprocessor", is an HTML-embedded scripting
  language.
• Much of its syntax is borrowed from C, Java and
  Perl with a couple of unique PHP-specific
  features thrown in.
• The goal of the language is to allow web
  developers to write dynamically generated pages
  quickly.

Ilker BEKMEZCI
PHP
3
Introduction-Example

• Different from CGI
• Different from Javascript.

lthtmlgt ltheadgt lttitlegtExamplelt/titlegt
lt/headgt ltbodygt lt?php echo "Hi, I'm a PHP
script!" ?gt lt/bodygt lt/htmlgt
Ilker BEKMEZCI
PHP
4
Configuration

• The configuration file (called php3.ini in PHP
  3.0, and simply php.ini as of PHP 4.0) 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.

Ilker BEKMEZCI
PHP
5
Security

• The configuration file (called php3.ini in PHP
  3.0, and simply php.ini as of PHP 4.0) 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.

Ilker BEKMEZCI
PHP
6
Four ways of Escaping from HTML

• 1. lt? echo ("this is the simplest, an SGML
  processing instruction\n") ?gt
• 2. lt?php echo("if you want to serve XML
  documents, do like this\n") ?gt
• 3. ltscript language"php"gt echo ("some editors
  (like FrontPage) don't like processing
  instructions") lt/scriptgt
• 4. lt echo ("You may optionally use ASP-style
  tags") gt lt variable This is a shortcut
  for "ltecho gt

Ilker BEKMEZCI
PHP
7
Comments
PHP supports 'C', 'C' and Unix shell-style
comments. lt?php echo "This is a test" // This
is a one-line 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
Ilker BEKMEZCI
PHP
8
Types

• PHP supports the following types array,
  floating-point numbers, integer, object, string.
• The type of a variable is usually not set by the
  programmer rather, it is decided at runtime by
  PHP depending on the context in which that
  variable is used.
• If you would like to force a variable to be
  converted to a certain type, you may either cast
  the variable or use the settype() function on it.

Ilker BEKMEZCI
PHP
9
Variables

• Variables in PHP are represented by a dollar sign
  followed by the name of the variable. The
  variable name is case-sensitive.

Ilker BEKMEZCI
PHP
10
Features-Creating/Manipulating images

• PHP is not limited to creating just HTML output.
  It can also be used to create and manipulate
  image files in a variety of different image
  formats, including gif, png, jpg, wbmp, and xpm.
• Even more convenient, php can output image
  streams directly to a browser.

Ilker BEKMEZCI
PHP
11
Features-Cookies

• PHP transparently supports HTTP cookies. Cookies
  are a mechanism for storing data in the remote
  browser and thus tracking or identifying return
  users. You can set cookies using the setcookie()
  function.
• Any cookies sent to you from the client will
  automatically be turned into a PHP variable just
  like GET and POST method data.

Ilker BEKMEZCI
PHP
12
Features-Connection Handling

• When a PHP script is running normally the NORMAL
  state, is active.
• If the remote client disconnects the ABORTED
  state flag is turned on. A remote client
  disconnect is usually caused by the user hitting
  his STOP button.
• If the PHP-imposed time limit is hit, the TIMEOUT
  state flag is turned on.

Ilker BEKMEZCI
PHP
13
Features-Persistent Database Connections

• Persistent connections are SQL links that do not
  close when the execution of your script ends.
• When a persistent connection is requested, PHP
  checks if there's already an identical persistent
  connection (that remained open from earlier) -
  and if it exists, it uses it. If it does not
  exist, it creates the link.
• An 'identical' connection is a connection that
  was opened to the same host, with the same
  username and the same password

Ilker BEKMEZCI
PHP
14
PHP vs. ASP?

• The biggest drawback of ASP is that it's a
  proprietary system that is natively used only on
  Microsoft Internet Information Server (IIS).
• ASP is said to be a slower and more cumbersome
  language than PHP, less stable as well.
• Some of the pros of ASP is that since it uses
  VBScript it's relatively easy to pick up the
  language if you're already know how to program in
  VB.

Ilker BEKMEZCI
PHP
15
PHP vs. PERL?

• Perl was designed to do a lot more and can
  because of this get very complicated.
• PHP has a less confusing and stricter format
  without losing flexibility.
• Perl is a very tried and true language, it's been
  around since the late eighties, but PHP is
  maturing very quickly.

Ilker BEKMEZCI
PHP
16
Questions
Ilker BEKMEZCI
TLI