Variables - Some Practice
In the previous section, you saw what variables are: storage areas
to hold things like numbers and text. You tell PHP to remember these
values because you want to do something with them. In this section,
you'll get some practice using variables. Off we go.
Testing variables with PHP
First, we'll take a look at how to display what's in your variables.
We're going to be viewing our results on a web page. So see if you can
get this script working first, because it's the one we'll be building
on. Using a text editor like Notepad, or your PHP software, type the
following. (You can copy and paste it, if you prefer. But you learn
more by typing it out yourself - it doesn't really sink in unless you're
making mistakes!)
<html>
<head>
<title>Variables - Some Practice</title>
</head>
<body>
<?php print("It
Worked!"); ?>
</body>
</html>
When you've finished typing it all, save the page as variables.php.
Then Run the script. Remember: when you're saving your work, save it
to the WWW folder, as explained here. To run
the page, start your browser up and type this in the address bar:
http://127.0.0.1/variables.php
Or this:
http://localhost/variables.php
If you've created a folder inside the www folder, then the address
to type in your browser would be something like:
http://127.0.0.1/FolderName/variables.php
If you were successful, you should have seen the text "It worked!"
displayed in your browser. If so, Congratulations! You have a working
server up and running! (If you weren't successful, make sure that your
server is up and running. If you're using easyPHP, you should see an
icon in the bottom right of your screen. It will be the letter "e".
A red square will be flashing, if the server is running.)
The PHP script is only one line long:
<?php print("It Worked!"); ?>
The rest of the script is just plain HTML code. Let's examine the PHP
in more detail.
We've put the PHP in the BODY section of an HTML page. Scripts can
also, and often do, go between the HEAD section of an HTML page. You
can also write your script without any HTML. But before a browser can
recognise your script, it needs some help. You have to tell it what
kind of script it is. Browsers recognise PHP by looking for this punctuation
(called syntax):
<?php ?>
So you need a left angle bracket ( < ) then a question mark ( ?
). After the question mark, type PHP (in upper or lowercase). After
your script has finished, type another question mark. Finally, you need
a right angle bracket ( > ). You can put as much space as you like
between the opening and closing syntax.
To display things on the page, we've used print( ). What you
want the browser to print goes between the round brackets. If you're
printing direct text, then you need the quotation marks (single or double
quotes). To print what's inside of a variable, just type the variable
name (including the dollar). Finally, the line of code ends as normal
- with a semi-colon (;). Another way to display things on the page is
to use an alternative to print() – echo( ).
Now let's adapt the basic page so that we can set up some variables.
We'll try some text first. Keep the HTML as it is, but change your PHP
from this:
<?php print("It Worked!"); ?>
To this:
<?php
print("It Worked!");
?>
OK, it's not much of a change! But spreading your code out over more
than one line makes it easier to see what you're doing. Now, it's clear
that there's only one line of code - Print. So add this second line
to your code (the one in red):
<?php
$test_String = "It Worked!";
print("It Worked!");
?>
We've set up a variable called $test_String. After the equals
sign, the text "It Worked!" has been added. The line is then
ended with a semi-colon. Don't run your script yet. Change the Print
line to this:
print($test_String);
Then add some comments ...
<?php
//--------------TESTING VARIABLES------------
$test_String =
"It Worked!";
print($test_String);
?>
Comments in PHP are for your benefit. They help you remember what the
code is supposed to do. A comment can be added by typing two slashes.
This tells PHP to ignore the rest of the line. After the two slashes,
you can type anything you like. Another way to add a comment, is like
this:
<?php
/* --------------TESTING VARIABLES------------
Use this type of comment if you want to spill
over to more than one line.
Notice how the comment begin and end.
*/
$test_String = "It Worked!";
print($test_String);
?>
Whichever method you choose, make sure you add comment to your code:
they really do help. Especially if you have to send your code to someone
else!
But you can now run the script above, and test it out.
How did you get on? You should have seen that exactly the same text
got printed to the page. And you might be thinking - what's the big
deal? Well, what you just did was to pass some text to a variable, and
then have PHP print the contents of the variable. It's a big step: your
coding career has now begun!
Exercise
Change the text "It Worked!" to anything you like. Then run
the script again. Try typing some numbers in between your double quotes,
instead of text.
Exercise
Change the double quotes to single quotes. Did it have any effect? Put
a single quote at the beginning of your text, and a double quote at
the end. What happens when you run the code?
Exercise
Delete the dollar sign from the variable name. Then run your code. What
error did you get? Put the dollar sign back, but now delete the semi-colon.
Run your code again? What error did you get, this time? It's well worth
remembering these errors - you'll see them a lot when you're starting
out! If you see them in future, you'll be better able to correct your
errors.
Now that you're up and running, we'll do some more variable work in
the next section.
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