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Introduction to Web programming with PHP

2012-2013

Course code EBS2040

Raoul Haenbeukers

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Whats this course about

Introduction to computer programming in general

(what is a computer language, what is PHP etc).

Practice with PHP

Practice with databases

Practice with dynamic web sites

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Todays lecture

What is this course about

Structure of the course

Examination

The website

Introduction to PHP

Brief introduction to HTML

Overview of Chapters 1 - 5

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Structure

First week well go through the book in 2 lectures

Study the covered material

Make all exercises

Practice in the Library (or at home any other place)

Second week: work on a project

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The Book

Larry Ullman

PHP for the web, fourth edition

Peachpit press

ISBN 0-321-73345-2

(Fourth edition is different from other

editions)

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Look at http://www.dmcinsights.com/phpvqs3/ for errata etc.

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Examination Two parts

Making all exercises, not graded Making one project, graded (four difficulty levels)

All exercises and projects can be found on the website for this course:

php.infonomics.nl All exercises and projects should be uploaded to that

server

Grades depend on the difficulty of the project (starting grades are 6, 7, and 8 for working projects according to the description), the bonus points obtained (+1 pt. max) and the way it is coded (in normal circumstances + or 1 pt.).

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Examination

Deadlines:

Monday, January 20th, upload all exercises before

17.00 hours

Before Monday, January 27th, upload your project before midnight, so Sunday 23.59 at the latest

It should be your own work! All the exercises and the project is individual work or

the result of group work in small groups, max 2 persons. (If project is the work of 2 persons, 1 point is subtracted from grade)

No unnoticed copying of code is allowed (plagiarism)

small parts of others may be used but this should be mentioned in the code

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Examination

Use our server to upload and test Please use our server to test your code

Do not use a separate server to test your code

In case of doubt we keep the right to organize a meeting to discuss the code and you should be able to explain what you have done.

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php.infonomics.nl

You will today receive an email with a username and password (password cannot be changed).

Needed to visit secured parts of the website, such as the forum

Needed to access the database

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The forum

See http://php.infonomics.nl, click on "message board", login with your private username and password (Note: do not use the faculty user-id and password)

The forum can be used to post questions and to give answers on material that is relevant for this course.

You can copy/paste code into the forum, no problem

This is the preferred channel of communication

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What will we do in this week?

Make the exercises

Write all code yourself, that is the only way to learn programming

Keep on track with the book chapters (next week, there is no time to read the book)

Be active on the forum, also by providing answers to questions posted by fellow students

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Next week

Work on the project in the reserved hours in the computer room (under supervision of staff members)

In the library

At home

Use the forum to ask/answer questions

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What is PHP

PHP is a recursive acronym and stands nowadays for "PHP: Hypertext Preprocessor", but originally it was called "Personal Home Page Tools". PHP is created by Rasmus Lerdorf.

PHP is attached (or embedded) to HTML such that you can create dynamic websites, that is, the content is created at the moment you retrieve that webpage

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Current situation

Basically PHP versus ASP.NET

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Sites running PHP

Examples of sites running PHP:

Wikipedia

Facebook

Wordpress

and many others

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A Simple example

HTML (Hypertext Markup Language) uses tags to define the structure of a page but all pages are already defined on the server and the user can only see these pages, follow hyperlinks etc. In pure HTML, there is no way to change the content of pages on the fly.

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Pure html

First simple example

This is my first simple html example

Example in a browser

(note that for the lectures I use a larger font size which is not in the HTML code above)

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PHP-HTML

First simple example


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PHP-HTML

Second simple example

Today, it is


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1 User clicks on a html link or types an address (URL)

Browser receives file, interprets

it and displays the contents

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GET http://www.infonomics.nl/index.html

Server looks for the

file (in this case

index.html) at a

specified place

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1 User clicks on a link or types an address (URL), now a php file

Browser receives file and displays the contents as HTML; The user cannot see that the file was created by PHP

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GET http://www.infonomics.nl/index.php

PHP request

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Use .php instead of .htm

If a web page includes a php script, you should always

give it the extension ".php" since otherwise, the script is

not passed through the scripting engine but directly to

the Webserver. For instance, if we call the second

example:

SecondSimpleExample.htm

than the resulting page would look like:

Second Example in Browser, named *.htm

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index.htm(l) or index.php

In most cases youll not specify a filename if you enter a web page or URL in the address bar.

For instance you specify php.infonomics.nl and not php.infonomics.nl/index.html

This is due to the default behaviour of the web

server. If you dont specify a filename, the file index.html (or index.htm, or index.php) is loaded automatically.

So index.htm(l) or index.php is treated as the

default filename and this file is always used as the main entry point of your web site.

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Short Introduction to HTML

the HyperText Markup Language (HTML) is created to format web-pages so they can be viewed by a browser.

The html language makes use of tags to structure the pages

a tag starts with a < and ends with a >

The most basic tag is the HTML-tag:

: start with html

: stop using html

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The next structure is the head and the body

The head contains header information, like the title of the page, the body contains the content itself

here comes the header information

here comes the body of the page

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Header info, the formal one (using XHTML)

Just make a copy and use it all the time!

Put your title here!

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The paragraph-tag defines paragraphs and should be closed by the "end-paragraph" tag .

A line break is presented by

(Note the -tag does not have a closing counterpart and is in xhtml written as )

The title is given in the tags.

Headings are within heading-tags, from 1 to 6: etc.

Example (also view source) 27

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It is very important to add comments to your pages since the enhance readability of the code. Moreover, during this course you should provide your name in the first line of all html and php pages.

In HTML, comment starts with

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One of the main features of web pages is that they can link to others. This is done by adding anchors. The general format is and but there should be some attributes in between. The main attributes is href="" which refers to another page (or email address etc).

Example:

link to the infonomics php server

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Opening a new browser window is simply done by adding the target= "_blank" attribute to the anchor tag:

link to the

infonomics php server in a new

window

Examples in a browser

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Finally, when using php you often want to get some input from users. This can be done by the FORM-tag. Examples are given in the "Introduction to HTML" page on the php.infonomics.nl web site, menu option: Course Material

Go

Also tables are often used to present data. Please also study the way how to create tables.

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To Do If you are not familiar with HTML, read

the "Introduction to HTML" section today and practice on the server or your own

computer.

How?

Create a new file, edit it with e.g. notepad, syn text editor, notepad++ or any other tool, rename it to name.htm, if you double-click on that file, the browser will start and youll see the result. (If you dont use php, you dont have to upload the page to the server)

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Adding PHP to HTML (Ch 1)

Escape from HTML into PHP can be done by including your code in the tag:

Everything in the tag is treated as PHP, at least if the file extension is .php

You can also switch between php and pure html in a single page by using more php-tags.

Example:

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Third simple example

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Adding comments It is very important that you add comments to your source

code. First of all we require that you write your name on the first line.

But if scripts become more complicated, you need to add

comments to explain what you do at that stage. This in order to make it easier to change the code afterwards.

Comments in html:

In php:

// single line comment

/* multiple line

comment */

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Output (Chapter 1)

By using echo or print

The output goes to the users browser (through an HTML file)

Echo can have multiple arguments:

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Output

Note that special characters need a special treatment.

For instance if you want to print a double quote ("), this can be cumbersome.

In that case, use an escape by adding a backslash to the character

E.g.: print "this is a \"quote\" from a text";

The escape actually means that the next character should be interpreted as a normal character without a special function

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Variables (Chapter 2) A variable is a container that holds data Variables always starts with a $-sign, followed by the name itself.

The name must always start with a character (A..Z, a..z) After the first character, you may use numbers and the underscore (e.g. $name1, $first_name etc.)

Variable names are case sensitive so $FirstName is different from $firstname

Always use logical names Use a consistent style, common is:

Camel style, e.g. $InterestRate, $DayOfTheWeek Underscores, e.g. $interest_rate, $day_of_the_week

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Variables: Examples

$name = Anton";

/* assigns the data (in this case a string, i.e. a piece of text) to the variable called $name */

$amount = 2.2;

/* assign the value 2.2 to the variable called $amount */ 39

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Variables: Summary

So All variables start with a $-sign The value is based on the most recent

assignment Assignment through the "=" operator Each statement ends with a ;

$my_num = "this is a string";

$my_num = 5; //this is an integer

print "$my_num"; //this prints a 5

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Types in PHP

Integer (whole numbers) Double (floating point number) String (sequence of characters) Boolean (have value TRUE or FALSE

(Chapter 6) Array (collection of other types)

(Chapter 7) Objects (not treated in the book or

course)

But PHP is very flexible! 41

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$a = 2; //an integer

$a = 2.2; //a double

$a = "two"; //a string

$a = FALSE; //a Boolean

Can be used after each other, of course the last assignment will be the one that is stored in the variable $a

Each of the above lines is called a statement and a statement is closed with a semicolon ;

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Common mistake

90% of all mistakes are caused by just one character, the:

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; Each statement ends with a ;

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Forms

Forms are used to pass information from the user to the program

The program can pass this information to a database, or use this information directly to e.g. calculate something etc.

We can have two files: one with the form and one that retrieves and handles the information.

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Forms

HTTP is stateless, no information is passed between HTTP requests so also not between several html or php pages

PHP forms do allow for passing information between pages

Get and Post, the basic methods to pass information between pages

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Forms in HTML

Form tag :

Input tag :

Attributes:

Form:

action= "filename.php", method = get or post

Input:

type=text, textarea, submit, reset, hidden

name : name of the input field

value : default value

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Forms in HTML

Example

(also have a look at the source code)

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Two methods: GET and POST

The GET-method passes information between pages by adding the variable names and values through the URL, e.g. mysite.org/page.php?name=Anton

View the code of the form

View the code of the php-program

View the result in browser

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Post is preferred

The data are posted in the body of the form

Variables are not visible

Larger amount of data

Cannot be book-marked

(Some firewalls block these data, but this has become rare)

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Post, an example

An example with radio-buttons.

(Radio buttons allow just one item to be checked, the others are un-checked automatically)

View the code of the form

View the code of the php-program

View the result in browser

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We have a form with

and an input field:

In the file result.php we can retrieve the passed information by using:

$fn = $_POST['firstname'];

Note the underscore and POST in capital

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Variable Types

Recall that a variable can be:

Integer (whole numbers)

Double (floating point)

String (sequence of characters)

Boolean

Array

Object (not treated here)

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Math functions by example

Pow(2,3) gives 8 (2^3)

Floor(2.5) gives 2

Ceil(2.5) gives 3

Round(2.5) gives 3

Abs(-2) gives 2

Min(2,3,4) gives 2

Max(2,3,4) fives 4

Exp(2) e to the power 2

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Using ++

In PHP (like C++) you are allowed to increment a variable with 1 by using ++. So:

$x = 1; //assign the value 1 to $x

$x++; //increment $x by 1

print ("$x"); //print $x, so a 2

This is similar to:

$x = 1; //assign the value 1 to $x

$x = $x + 1; //new x is old x plus 1

Print ("$x"); //print $x, so a 2

The same holds true for -- (decrement by 1)

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Strings

Strings: a collection of characters enclosed with single or double quotes.

PHP has many string functions to manipulate strings

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Concatenation

Adding two strings together is simple done by a dot-operator

$firstname=Anton";

$lastname =Corbijn";

$name=$firstname . " " . $lastname;

print("$name");

/*will print Anton Corbijn (note the

space we have added)*/

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Many useful string functions

Strpos(string, stringtofind) gives the position of the first instance of stringtofind in string, starting at 0

E.g. strpos("Rasmus","u") returns a 4

Strlen gives the length of the string

Substr(string,pos) returns the substring of string, starting at position pos (actually pos+1)

E.g. substr("example",5) returns "le"

And many other string functions (see chap 5) or even more at: http://www.php.net/manual/en/ref.strings.php

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Addslashes and Stripslashes

Two functions are very useful if we want to store data in a database. As we will see Wednesday, adding a single quote in a text to a database is problematic, for this reason we use these two functions.

Addslashes adds slashes to all kinds of special characters and stripslashes removes them

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Example

Suppose you want to store the name: Jeanne dArc in a database or the text: he said: PHP is very powerful. In both cases PHP has some troubles, for instance look at:

$text = "He said: "PHP is very powerful. "";

This is impossible since PHP assumes that the string finishes after the second ".

The solution is to add slashes:

$text = "He said: \"PHP is very powerful.\""; But if the data come from the input of a user, e.g. by using a form, we dont know in advance where to put the slashes. The function addslashes does this for us.

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Addslashes

So if you want to store text in a database and this text comes from a form (by using POST) we can have:

$inputtext=$_POST['text'];

$text=addslashes($inputtext);

Which is equal to (note the double use of the variable $text):

$text=$_POST['text'];

$text=addslashes($text);

And this also can be done in one line:

$text = addslashes($_POST['text']);

//now save $text in the database

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Final remarks

Be active on the Forum

Make all exercises (required!!)

Try to understand the book by typing in the examples, changing them a bit etc.

Programming is not just reading but also doing

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Try it: today

As part of the exercises today you are asked to create some simple files and to upload them to the server.

Try it and do not hesitate to ask questions on the forum if things are not working

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Documents