Tutorial: A Complete Beginner's Guide to PHP

[jackfranklin]

Ok. You’ve got a basic knowledge of HTML and preferably CSS. Where now? It has to be something dynamic next! You have a choice of ASP, Javascript and PHP.

Why Choose PHP?
PHP is a loosely typed language. Simply put, it’s not so strict with the way you code it. One tiny error is not likely to throw the entire script off.

The Very Very Basic PHP
All PHP goes inside tags.
Start tag:

PHP Code:

<?php

End Tag:

PHP Code:

?> 


Firstly, don’t worry. I’m not going to show you how to do that boring ‘Echo World’ statement over and over. Let’s say we want to be able to work out the Area and the Perimeter of a rectangle. Data in PHP (Number or Text) are best stored in variables. [NOTE: A List of Items is best stored in an array, but we will see that a bit later on].

The variable sign in PHP is the dollar sign on your keyboard (Above the 4). ‘$’. You then place the name of your variable after it. Example:

PHP Code:

$width 


You then need to give this a value. You need to use a single equals sign after it. This is were the ‘loosely typed’ bit comes into play. You can either use:
$width= OR $width =
Personally, I always place a space around the ‘=’ so it’s easier to read, but it’s your choice. [NOTE: If you leave a space before the ‘=’ it’s always best to leave one after it as well. Also, choose your favourite way and stick with it don’t switch from one to the other]
Ok, back to our rectangle. The rectangle will have 2 values which will change, the width and the height. So, we just create our two variables.
[NOTE: From now on in this tutorial I’m going to put spaces around my ‘=’ but if you don’t want to you don’t have to, just change it.]

PHP Code:

$width = 
  $height = 


Let’s say, this rectangle has a width of 5 and a height of 2.

PHP Code:

$width = 5; //This is the width of my rectangle
  $height = 2; //This is the height of my rectangle. 


Woah! There are a couple of things to look at there!
Firstly, note the ‘;’ after each line. This is needed after you declare the variable to tell PHP that that variable is finished, you have stopped declaring a value for that variable. Secondly, note the ‘//’ and then a comment. This is the PHP way of declaring comments. You know, in HTML you use <!—Comment-->, well in PHP you just place the ‘//’ in front of your comment.
So, now our rectangle has a width and a height, we can work out the area and the perimeter. The area is the width multiplied by the height, and the perimeter is the Width, add the height, add the width, add the height, or in other words, (Width + Height) multiplied by 2. So, how can we do this in PHP? Let’s take a quick look at PHP Operators!
Operators, or at least what I take as operators, are PHP’s way of dividing, multiplying, etc. Below are a list of Operators and what they do. I advise you learn these, they are not all what you expect:
Addition – (+)
Subtraction – (-)
Multiplication – (*)
Division – (/)
Modulus – (%)
Addition by One – (++)
Equal To – (==)
Not Equal to – (!=)
Less Than – (<)
More Than – (>)
Less Than or Equal to – (<=)
More Than or Equal to – (>=)

Note that Equal to is a double ‘=’ not just a single one. This is because a single equals sign is a ‘giver’ – it gives something a value. EG: $variable = 2.

So, back to our rectangle, to work out the area we will need to use multiply (*) and to work out the Perimeter, we will need to use Add (+) and Multiply (*).
I’m going to create 2 new variables, $area and $perim.

PHP Code:

$area = 
  $perim = 


Now, to work out the area, we multiply $width and $height.

PHP Code:

$area = $width * $height; 


The perimeter is ($width + $height) * 2. This can be done in PHP. You are still able to use brackets.

PHP Code:

$perim = ($width + $height) * 2; 


So we now have worked out the area and perimeter. But, we want to show these to our user! In PHP, to display something, you use echo.

PHP Code:

echo 'The area of our rectangle is: '.$area.' and the perimeter is: '.$perim.' We worked them out using Operators!'; 


You surround the entire echo statement in ‘ and ‘. All the text, including any HTML tags, need to be surrounded by ‘’. To display a variable, this is how you would.

• You have a simple echo statement:
  PHP Code:

  echo '<p>What is the width of my rectangle?</p>'; 

• To add a variable in after the question mark, firstly you need to add a single speech mark (').
  PHP Code:

  echo '<p>What is the width of my rectangle?'</p>'; 

• Then add a full stop:
  PHP Code:

  echo '<p>What is the width of my rectangle?'.</p>'; 

• Now add your variable name, another full stop, and another single speech mark.
  PHP Code:

  echo '<p>What is the width of my  rectangle? '.$width.'</p>'; 

• In simple terms, all variables in echo statements must be surrounded with a: ‘. and a .’

But there is an exception. If you only want to display a variable with no text you do it like so:

PHP Code:

echo $width; 


Easy as that!

So, we can now show off to the user. See if you can, on your own, display the width, height, area and perimeter in echo tags, each in a <h4> tag with ‘Width is: ‘ before them. (Replace width with whatever). See below for the answer.

PHP Code:

echo '<h4>Width is: '.$width.'</h4>';
  echo '<h4>Height is: '.$height.'</h4>';
  echo '<h4>Area is: '.$area.'</h4>';
  echo '<h4>Perimeter is: '.$perim.'</h4>'; 


That’s it!

[jackfranklin]

More - I went over the post limit.
Arrays
Nearly there! Remember earlier I mentioned a list going in an array? This is how.
An array is simply a list of items. To create an array you do the following:

PHP Code:

$worker[0] = "Jack";
$worker[1] = "Ed";
$worker[2] = "Alex";
$worker[3] = "Rob"; 


This creates a list of items. The variable $worker is now an array. [NOTE: That the first item is not the ‘1st’ but the ‘0th’. To display them, you just echo them like we did above:

PHP Code:

echo $worker[0]; //Displays Jack 


PHP Code:

echo 'One of the workers is called: '.$worker[2].' He is a nice worker'; //Displays: One of the workers is called Alex He is a nice worker. 


Happy?
That is indeed the basics of PHP covered as simply as I can put.