 |
 |
 |
 |
|
|
|
Loops & Decisions in PHP - The ABC's of PHP Part 8
Introduction
In any given computer language (PHP is no exception) there has
to be a way to allow the running code to decide between doing 2
different things.
If there wasn't then software would not be able to adapt based
on operating conditions, or it wouldn't be able to decide
between two different users.
In most languages the most basic of these is the
"
if" statement, which as its name implies does
something if a given condition is true.
Let's look at a quick example:
$name = "peter";
if($name == "peter")
{
print "Hello peter how are you today?\n";
}
else
{
print "Sorry I don't know you\n";
}
As you can see it's very simple. First we have a string variable
that holds a name. Then we have the "
if" statement which says
'if the variable called name holds a value that is equal to
peter then perform the program lines in the first set of curly
brackets, otherwise perform the commands in the second set of
brackets'
The first question you might ask is why do we have a double ==
sign, good question. This is because in PHP everything in a
decision has to result in either true or false, and since we use
= to give a value to a variable, then = will always be true
(trust me, computers work that way ;-) ) and thus we would not
be able to get a false. There are some cases where you have to
use === (3 = in succession) but for most of the time == will do
just fine.
Other Checks?
We don't just have to check to see if two values are equal, we
can also check to see if they are not equal, or greater than and
less than, the following list shows the different operators
'
if' understands:
- == - Are variables equal ( $A == $B )
- != - Are variables NOT equal ( $A != $B )
- >= - Is variable 1 greater than or equal to variable 2 ( $A >= $B )
- <= - Is variable 1 less than or equal to variable 2 ( $A <= $B )
- > - Is variable 1 greater than variable 2 ( $A > $B )
- < - Is variable 1 less than variable 2 ( $A < $B )
You can also group one or more decisions together by using
normal brackets, separated by any of the Boolean operators as
shown below:
- && - AND (Both decisions must be true)
- || - OR (Either of the decisions must be true)
These are typically used in the following way:
$fname = "peter";
$lname = "shaw";
if( ($fname == "peter") && ($lname == "shaw") )
{
print "greetings Shawty, you are allowed in…";
}
else
{
print "be-gone stranger, you are banished from here…";
}
This is now saying that
fname must be equal to
"peter" AND lname must be equal to "shaw" before I
allow the top code to run, if not then the bottom code will run.
The full range of operators can be found in the php manual here and as always I strongly encourage you to read and
experiment with different combinations.
[ Next Page ]
| Comments: | ||
No Messages FoundYou can post questions/corrections/feedback here
| ||
|
If you are looking for help, please post on the appropriate forum here. Your questions will be answered much more quickly. | ||
