This post is
part 3 of the Basic PHP Crash Course. If you have never red before this Crash Course, you should read
part 1 and
part 2 first.
Before enhancing our site, I want to explain you about the function.
What is a function?
A function is a block of code that has a name. It is not executed when we load
the page. We need to call its name when we need to execute that block of code. And then we can call any time whenever we need it.
If you have some code that need to use many time, you should use as the function.
The function name can start with a
letter or
underscore (not a
number)
To understand the idea of function, we need to create our own simple function.
Simple Function
Let's start with the hello world function.
<?php
function hello()
{
echo "Hello World!";
}
hello();
?>
Function with parameter
Parameter is a variable that we send to our function to use withing our function.
<?php
function hello($name)
{
echo "Hello ".$name;
}
hello("Jack");
?>
Function with return value
Return value is a variable that return from our function.
Sometime we need a return value
<?php
function add($a,$b)
{
$result = $a + $b;
return $result;
}
$total = add(5,3);
echo $total;
echo add(3,5);
?>
We can use the return value like above example and like int our web site.
Enhancing our site
There is no need to
change in our index.php.
For our
process.php,
we need to test whether the user fill the form data or not. To
determine whether a variable is set, we will use isset() function. In
PHP, there are many built-in functions. I create a tutorial about this here.
Following is our new process.php
<html>
<head>
<title>Order Process</title>
</head>
<body>
<?php
if($_POST['submit']=='Submit Order')
{
if( isset($_POST['cus_name']) && isset($_POST['quantity']) && isset($_POST['address']) )
{
$cus_name = $_POST['cus_name'];
$quantity = $_POST['quantity'];
$address = $_POST['address'];
?>
<p>Thank <?php echo $cus_name; ?> !</p>
<p>You order <?php echo $quantity; ?> pizza.</p>
<?php
$total = $quantity * 10;
?>
<p>It will cost you <?php echo $total; ?> $.</p>
<p>We will send withing 2 hours to <?php echo $address; ?>.</p>
<?php
}
else
echo "You need to fill all data";
?>
<?php } ?>
</body>
</html>
Explanation
Let's talk about isset() function.
We will pass at least one parameter and it will return boolean true or
false. It will return TRUE if var exists; FALSE otherwise.
Logical Operators
If you need to combine the results of logical conditions, you must be use logical
operators.
Following
table is PHP logical operators.
| ! | NOT |
| && | AND |
| || | OR |
| and | AND |
| or | OR |
| xor | XOR |
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