Introduction
Syntax
Variables
Keywords
Data Types
Relational Operators
Conditional Statements
Processing Forms for and while loops security
Based on Rasmus Lerdorf& Kevin Tatroe: Programming PHP. Sebastopol: O’Reilly, 2002.
W05/161B/Daniel Sauter

Simple yet powerful language designed for creating dynamic web content .
Mainly used to output HTML , however, any document format can be generated (supports PDF files, GIF, JPG, and PNG images, Flash movies, XML)
One of PHP’s main features is its wide-ranging database support
(e.g. MySQL , PostgreSQL, Oracle, Sybase, ODBC) note: this class will focus on the use of PHP to output HTML/XML and MySQL creating dynamic web content

Rasmus Lerdorf first conceived PHP in 1994 as Personal
Home Page Tools (PHP Tools)
Originally written for a project at the University of Toronto to represent data from various places in a web interface with PHP 3.0 it developed from a one-person effort to an open source project with developers around the world
PHP3 supported all major operating systems, databases and developed to a complete scripting language.
In Dec. 2005, 22,172,983 Domains, 1,277,375 IP Addresses used PHP

The TIOBE Programming
Community index gives an indication of the popularity of programming languages.
The ratings are based on the world-wide availability of skilled engineers, courses and third party vendors.
The popular search engines
Google, MSN, and Yahoo! are used to calculate the ratings.
Observe that the TPC index is not about the best programming language or the language in which most lines of code have been written.
Source: http://www.tiobe.com/ tpci.htm, checked Feb. 17 2006

PHP is strongly influenced by other programming languages, therefore the concepts behind the lexical structure of PHP can be easily applied to other languages, e.g. ActionScript, Java or
Processing.
PHP is not case sensitive, all three lines are equivalent: echo(”hello!”);
ECHO(”hello!”);
EcHo(”hello!”);
As in HTML, whitespace doesn’t matter in a PHP program, you can spread statements across any number of lines or put them in a single line.

Elements of the language and how they are structured.
- Statement
- Statement terminator
- Function (Command)
- Parameter
- Comments
// Program to write my name
$name = "Daniel"; echo($name);

- are used to store values
- always begin with a dollar sign ($)
- have a name/identifier and a value
- are case-sensitive
- must not begin with special characters or number, no space.
$name = "Daniel"; // Declare and assign
$number = 32; // Declare and assign
$counter = 12; // Assign variable echo($number); echo($name); echo($counter);

The scope of variables determines which parts of the program can access it. The scope changes depending on the location of the variable’s declaration. There are four types of variable scope in PHP:
- global (can be accessed anywhere in the program)
- local (as part of a function)
- static (retains its value between calls of a function)
- function parameter (only accessible inside the function)
We’ll start by using predominantly global variables.

A keyword is a word reserved my the PHP programming language for its core functionality. You cannot give a variable, function, or class name the same name as a keyword.
Selected keywords are for example: and, not, or do, for, while if, else, elseif, switch new true, false eval return
...

20038, -33, 2 // Integer, whole numbers
3.1254, 0.1 //Floating Point, numeric values with decimal digits
‘hot dog’, “Daniel” // String, sequence of characters false, true, 0, “” // Boolean, “truth value” of conditional statement
$person = array(’Jeff’, ‘Daniel’, ‘you’); // Array, group of values
$person[0] = “ Jeff”;
$person[1] = “Daniel”;
$person[2]= “you”;

Used to compare values:
> (greater than)
< (less than)
>= (greater than or equal to)
<= (less than or equal to)
!= (inequality)
== (equality)

5 > 4 // True
5 < 3 // False
5 > 5 // False
5 >= 5 // True
5 >= 6 // False
5 != 5 // False(not equal)
5 == 5 // True
5 == 4 // False

Used to make decisions about which code to execute and which to ignore. E.g.:
$num = 5; // assigning the value if($num < 10) { // if condition is true echo("Less than 10"); // this line is executed
}
$num = 5; if($num < 10) { echo("Less than 10");
} else if($num > 10) { echo("More than 10");
} else { echo("Equal to 10");
}

note: in order to understand PHP quickly and effectively, a good understanding of HTML is required.
Because PHP and HTML code is mixed within the Code, knowing exactly what belongs to which language is essential
This is increasingly important in the process when JavaScript or CSS elements are added
Please continuously refer to Web Design in a Nutshell (Jennifer
Niederst) to revisit concepts of HTML, JavaScript and CSS if required.

Use echo to put a string into the HTML code of a PHP generated page. Both statements are equivalent.
echo “A message for the browser”; echo (”A message for the browser”);
Echo’ing a variable echo $variable;
Echo looks and behaves like a function, in fact it is a language construct, which means that you can omit the parentheses which all functions need.

process.php:
<html>
<body>
<?php
$birthday = $_POST['birthdate'];
?> echo "Your birthday: $birthday";
</body>
</html>

input.html:
<html>
<body>
<form action="process.php" method="post">
<input type="text" name=" birthdate ">
<input type="submit" value="send birthdate">
</form>
</body>
</html> process.php:
<html>
<body>
<?php
$birthday = $_POST['birthdate']; echo "Your birthday: $birthday";
?>
</body>
</html>

Using PHP:
1. Using PHP, Write ‘hello world’
2. Make a form with one input field and a submit button. After submitting, write the content of this input field on the screen, and, the input field as mentioned before.
3. Use the html document you created earlier (including a popup menu, a checkbox, a text area, etc. Write all contents/ values of these forms onto the screen.

Controls a sequence of repetitions. A for() structure has three parts: init , test , and update . Each part must be separated by a semi-colon ";". The loop continues until the test evaluates to false.
When a for() structure is executed, the following sequence of events occurs:
1. The init statement is executed
2. The test is evaluated to be true or false
3. If the test is true, jump to step 4. If the test is False, jump to step 6
4. Execute the statements within the block
5. Execute the update statement and jump to step 2
6. Exit the loop.
for ($i = 1; $i <= 10; $i++) {
echo $i;
}

The while structure executes a series of statements continuously while the expression is true. The expression must be updated during the repetitions or the program will never "break out" of while().
$i = 1; while ($i <= 10) {
echo $i++;
}

Using HTML and PHP:
1. Create an html page including a form and a text filed, name it amount.html
2. based on the value provided in amount.html, create a for loop which prints the variable’s value and a text message as many times as the value submitted by the user.

If the ‘register_globals’ option in the PHP setup is activated
(php.ini), PHP creates a separate global variable for every form parameter.
This functionality is both convenient and dangerous, as it lets the browser provide initial values for those variables, which makes the system vulnerable to attacks and it presents a security problem.