In the previous page we covered
the basic structure of if and else statements. This page
will cover in greater detail various modifications for the
if and else statements.
Conditional Operators
All of this time I have been using conditional operators
such as == to determine whether a condition is true or not.
But I never elaborated on what the various conditional
operators are, and how they can be used to see if something
is true or not. I think now is a good time to explain that.
The following table lists the more popular conditional
operators you can use in PHP:
|
Operator |
Description |
|
== |
Equals |
|
>= |
Greater than or
Equal |
|
<= |
Less than or
Equal |
|
> |
Greater than |
|
< |
Less than |
|
!= |
Not Equal |
An example using something other than the equals
conditional operator could be:
- <?php
- $num
= 5;
- if
($num
> 4)
{
- print("Number
greater than 4.");
- }
- ?>
In the preceding example we used the greater than ( > )
operator that compares whether the variable $num is greater
than 4. Since 5 is greater than 4, the statement is true,
and the code will be executed.
If you were to replace the greater than operator ( > ) in the
above code with the not equal ( != )operator, the code will be
true also. 5 does not equal 4, and that is true!
Logical Operators
Throughout this tutorial, our If statements depended on only
one condition. If that one condition was true, the code
would executed. Let's introduce logical operators that will
allow you to set multiple conditions.
The operators that you will use frequently is AND and OR.
|
Operator |
Description |
|
&& |
And |
|
|| |
Or |
|
and |
And |
|
or |
Or |
Here is a PHP example using one of the logical operators:
- <?php
- $username
= admin;
- $password
=
password;
- if
(($username
== admin)
&&
($password
==
password))
{
- print("Access
granted!");
- }
- ?>
The first condition checks to make sure that $username
equals admin. The second condition checks to make sure that
$password equals password. The logical operator && checks to
see if both condition statements are true.
If your value for password changed, the condition would
fail. Even though one condition is true, because the &&
logical operator needs BOTH conditions to be true, the test
fails. If you used the || operator, all you would need is
for one condition to be true. Needless to say, if both
conditions fail, && and || will not help make your
statements true.
If/Else
Statements
