Week 5: Intro to programming and PHP

HTML and CSS are not programming languages. HTML is a markup language and CSS is a style sheet language. They dictate where things go and how they should look, but they can’t actively do things.

PHP is a server side scripting language. It can be used to actually do things. When you’re writing PHP, you’re really programming!!

But! You need a server to run PHP. PHP, as a scripting language, needs to be executed by a server. If you write PHP into your website and then just open the file in a browser, it won’t work. The server does all the legwork – PHP is just a set of instructions to tell the server what to do.

Using the QUT Server Space

When logged in to a computer at QUT, you can access your public_html folder from windows explorer or finder. In here you can change files and immediately see the results by visiting student.ci.qut.edu.au/~yourusername.

  • You access your public_html file on a mac by opening Finder, pressing command-k, and typing in smb://cif-smb.qut.edu.au .
  • In windows, just type \\cif-smb.qut.edu.au into the address bar in explorer.

Testing your PHP code at home

You can simulate a server space at home using :

Introduction to Programming Concepts:

Programming today is based around the concept of Object Oriented Programming.

This indicates that your software is made up of objects – the building blocks of any logical system. These objects are Functions and Variables. Once you have declared a function or a variable, you can use it throughout your code. These principles apply to basically every programming language you’re ever likely to use.

Variables

A variable is a stored piece of information. It could be a number (an integer or floating point number) a word or series of words (a string), or a yes/no value (a boolean). A variable has both a value and a name. For example, I might have a variable called firstName with a value of “Cassie.” Or a variable called visitorCount with a value of 10. Once I have a variable, I can use it as if it were the value. For example, I could say something like:

$visitorCount = 10;

$newNumber = $visitorCount +1;

then the variable newNumber would equal 11.

In PHP variables always have a $ in front. Different languages have different conventions for using variables. In some languages you have to specifically say whether your variable is an integer, string, boolean, etc. In PHP, you don’t!

Functions

A function is a piece of code that does something. It will change something, or return a value. Functions have names. Once you define a function, you can use its name to call it at any time.

A function has a name and a body. The body of a function consists of the lines of code that actually do whatever it is you want to do. For example, I might have a function like:

function sayHello() {

echo “hello”;

}

If I wanted to use this function anywhere in my code, because I have defined it with the name sayHello(), I can simply write printHello() and the code in the body of the function will execute. Even though in this example the function is simple, this is good because a function may consist of multiple lines of code which you obviously don’t want to write and re-write many times – instead you can just use the name. This is a function call.

A function can have parameters and a return value. Parameters are variables that can be given to a function, in order for it to do something with them. A return value is a variable it might return when it is complete. It can have many parameters or no parameters, it can have no return value or one return value. A function cannot have multiple return values, however.  For example:

function increaseVisitorCount($currentCount){

$newCount = $currentCount+1;

return $newCount;

}

were I to call this with increaseVisitorCount($visitorCount);, I would get a number back. So if I wanted to use a value to get a number, I could write something like:

$visitorCount = 1;

$visitorCount= increaseVisitorCount($visitorCount);

This would set the variable visitorCount to be the return value of increaseVisitorCount – in this example, it would become the number 2.

Built in Functions

Various programming languages have built in functions. For example, I can say print(“Hello”);, print() is a built in function of php. I don’t have to define a new function called print(), because one already exists. That being said, it also means I should be careful not to define my own function named print(). print() is already taken, so it won’t work. You should always give your functions specific names so you know what they do and so they don’t clash with any built in functions.

Those are the basic structures behind programming. 

We will step through examples of how these work in class.

Some specific examples are in this file: PHP Beginner Examples. (right click and save file as)

General programming resources

PHP Resources:

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