PHP: Making the Internet Yours

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PHP Making the Internet Yours
Kiel Howell Neil Farland Michael Schroeder
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Introduction

• PHP is an interpreted language. The code is run
  directly from the file, uncompiled just like
  Python.
• PHP is used on many operating systems and
  architectures, though we used CentOS for our
  demonstrations.
• PHP provides extensive extensions, including
  documentation, on the official website
  http//www.PHP.net/ .

• PHP Hypertext Preprocessor is a fairly new
  language, evolving from a set of Perl scripts
  into the language to beat for creating
  interactive websites.
• PHP is also useful in developing server-side
  applications, such as interfacing with a database
  via a web page.
• Often seen on Apache or Linux servers,
  interacting with SQL databases. Together with
  PHP, this forms the LAMP (Linux, Apache, MySQL,
  PHP) architecture, a very common server setup.
• PHP is an open-sourced language. Many
  programmers contribute to PHP, leading to a wide
  array of important contributions and, sometimes,
  increased ambiguity in syntax.

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History of PHP

• Created in 1995 by Rasmus Lerdorf, as Personal
  Home Page / Forms Interpreter, or PHP/FI. It
  was not a true language yet rather, it was a set
  of humble Perl scripts.
• Was expanded upon through the open-source
  community, mostly using C to allow for
  communication with databases and creation of
  dynamic content.
• PHP/FI 2.0 and PHP 3.0 were released in 1997,
  the latter written by Andi Gutmans and Zeev
  Suraski for the creation of eCommerce websites.
• PHP re-named to PHP Hypertext Preprocessor.
• PHP 3.0 was extremely extensible and
  communicative, with stronger syntax and better
  object-oriented programming capabilities.

Rasmus Lerdorf
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History of PHP (cont)

• In winter 1998, Gutmans and Suraski begin
  rewriting PHP from the ground up, aiming to
  improve performance and modularity. This became
  the Zend engine in 1999, named after a fusion
  of their first names.
• PHP 4.0, based on the Zend engine, was released
  in 2000. It was far more efficient, had wider
  support for web servers, output-buffer
  capability, enhanced security for user input, and
  multiple new constructs.
• PHP 5.0, still based on the Zend engine, was
  released in July of 2004 and remains the most
  current iteration. New to this version stronger
  exception handling, a Standard PHP Library (SPL),
  enhanced XML support, greater object-oriented
  programming, embedded SQL Lite and SimpleXML.

Andi Gutmans
Zeev Suraski
Purpose of PHP

• PHPs purpose is simple Web design. Its server
  side, cross-platform, HTML-embedded, all to
  further web design.

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SQL

• SQL (Structured English Query Language) is the
  widest-used relational database language. It is
  easily learned, used, and maintained as anyone
  who has taken Intro to Databases knows.
• SQL is not Turing complete, though it has a
  grammar, a syntax, programmatic purpose and
  intent.
• SQL (or, rather, MySQL or PostgreSQL) is
  embedded into the code of PHP, and are often used
  hand-in-hand much of what is done with PHP is
  simply displaying database results in a pleasant
  manner.

Apache

• Apache is a free, open-sourced, cross-platform
  project used for many web servers today. It
  allows for authentification against DBMS
  databases and GUIs, and is the most common web
  server used with PHP (and in general).

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Variables

• PHP variables are indicated by a dollar sign
  that is, the first character in any variable name
  must be . Variables need not be formally
  declared, and are loosely typed.
• Variables in PHP are of dynamic scope. If
  declared within a function, a variable can only
  be accessed within that function, unless
  specifically declared global. If declared within
  a class, the variable is visible and usable by
  all functions within that class. Variables
  declared outside of functions and classes are
  global.
• Variables are case-sensitive, although keywords
  and functions, both user- and built-in-, are not.
• All variables can be tested as a Boolean.

Basically, beyond the initial , you can work
with PHP variables just as you would work with
variables in Python.
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Data Types

• PHP supports a few primitive data types
  Integers, Floating point numbers, strings,
  arrays, and booleans.
• PHP strings are dynamic in length, and built-in
  to the core code of PHP. They must be surrounded
  by double quotes like this to be recognized as
  a string. You can use variables and HTML within a
  string, as in the previous example.
• PHP arrays, like other variables, must begin
  with the . Individual elements can be accessed,
  as PHP arrays work much like Python dictionaries.
  PHP 5.0 allows for easy iteration over arrays.

Comments

• Comments are handled just like in C or as in
  Python.

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Functions and Decisions

• Functions and decisions are, again, used much
  like in other languages. PHP functions, both
  user-made and built-in, will be very familiar to
  Python programmers, whereas the decision
  statements (If, While, For) are ripped straight
  from C.

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Input/Output

• Because PHP is designed to build web pages, a
  user has to have a web page to input information
  into (also, a .php file, when run, creates a
  .html file to display its results). Because of
  this, anything more advanced than the previous
  examples requires at least some knowledge of
  HTML. Forms, buttons, text boxes, and the like
  are all necessary tools. Things like CSS,
  Javascript, et al are not necessary, but are
  helpful in making anything truly complex and/or
  pretty.

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Exception Handling

• There is no try/except duo in PHP, so you have
  to use an if-correct, else-error setup wherever
  you expect errors to pop up (such as getting a
  string when asking for numbers).
• In that else-error section, you can use the
  built-in die() function to make the script print
  out an error message and quit running.

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Object-Oriented PHP

• PHP only became somewhat object-oriented with
  version 3.0, and only strongly so with the most
  recent revision, 5.0 . Below is a simple example
  of a class.

• PHPs classes and functions work very similarly
  to those of other languages.

Example of a Car class mostly stolen from
Wikipedia. It was too perfect to not.
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Libraries

• PHP has a number of libraries already built into
  it, so theres no need to reinvent the wheel.
  Weve nowhere near the time required to talk
  about them, so well simply list them (thanks,
  Wikipedia, for the list!).

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(Possibly) Cool Examples of PHP

• We have to minimize the Powerpoint to show you
  the stuff we did with PHP, so hold on a second
  while we poke around and load it up.

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Whats Not So Great About PHP?

• Variables dont have to be initialized, and
  theres no strict type-checking.
• There may be too many (3,000!) built-in
  functions, with quantity destroying quality. Some
  consider it impossible to effectively code in PHP
  without a resource at-hand.
• Older built-in libraries and functions do not
  use any standard format for their names (IE,
  noun_verb(), verb_noun(), studlyCaps() and
  under_scored() ), though newer libraries do
  follow a standard.
• PHP has significant security issues regarding
  cross-site scripting and default variables.
• PHP can be so uniquely configured to one
  particular server that code written for that
  server cannot be ported elsewhere.
• PHP5 is not totally backwards-compatible with
  PHP4.
• Not all libraries and extensions are thread-safe.

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Any Questions?
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References
"PHP Hypertext Pre Processor." PHP. 20 Apr.
2006. 5 Mar. 2006 . Sebesta, Robert
W., and Robert W. Sebesta. Concepts of
Programming Languages. 6th ed. Boston, MA
Addison Wesley, 2003. Wales, Jimmy. "Wikipedia".
3/10/06 . Williams, Hugh E.
Web Database Applications with PHP MySQL. Ed.
David Lane. 2nd ed. Sebastopool, CA O'Reilly,
2004. Welling, Luke, and Laura Thomson. PHP and
MYSQL Web Developments. 3rd ed. Indianapolis, IN
Sams, 2005.