If/else statements are very useful because they allow
your code to be expressed in certain situations but not in
others. You can control when those situations occur by using
control statements such as if/else.
Before we delve any further, a basic If / Else statement in
PHP looks like the following:
- <?php
- if
(true)
{
- do something
- }
else
{
- do
something else
- }
- ?>
Simply put, if a condition happens to be true, the code
in pink will be executed. If the condition happens to be
false, the code in orange, will be executed. The Else
statement is optional though. If you do not specify an Else
statement, your code will not do anything if the condition
happens to be false.
For example, here is the code without an Else statement:
- <?php
- if
(true)
{
- do something
- }
- ?>
Let's take an example involving a robot called kirupaTron
that is programmed to do among many other things, cross a
busy intersection.
kirupaTron is at an intersection. He is programmed to wait for the Walk light
before crossing the intersection. Once kirupaTron sees the
Walk light come on, he knows it must be safe to cross the
intersection. The logic behind his action is controlled by
an If / Else statement.
The robot checks to see IF the Walk light turns on. If
the Walk light is on, the robot decides to walk. IF the walk
light is off, the robot decides to stay put. Lucky for us,
kirupaTron is programmed in PHP, and the code that helps him
at intersection looks like the following:
- <?php
- if ($light
== "Walk")
{
- print("kirupaTron
- start walking.");
- } else
{
- print("kirupaTron
- don't walk.");
- }
- ?>
The above code is a simplified form that is similar to
what is displayed above. If the variable, $light is set to
Walk, the condition becomes true, and therefore, the
code will execute. If the $light is set to something other
than Walk, the condition fails, and the code for not walking
will execute.
For example, copy and paste the following code into a new
PHP document:
- <?php
- $light
= "Stop";
- if
($light
== "Walk")
{
- print("kirupaTron
- start walking.");
- }
else {
- print("kirupaTron
- don't walk.");
- }
- ?>
When you preview the page containing the above code, you
will see that the text for not walking is displayed. But
why? The condition for the if/else statement to be true is
when $light equals "Walk". Since in the previous line, we
mention that $light equals "Stop", the condition fails.
Therefore, the code for not walking executes.
Now, let's say you want to make the condition true.
Well, in that case, replace the "Stop" with "Walk." Your
first line of code should look like the following:
- $light
= "Walk";
Now, test your page again. You will find that the code
for for walking is displayed. The condition is true.
The reason the condition is true is because the variable
$light does equal "Walk."
In the next page we will cover
more about if and else statements such as conditional and
logical operators.
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If/Else
Statements
