PHP - English

PHP if … else if Statements

 

 

You can also add “else if” parts to the If Statements you’ve been
exploring in the previous sections. The syntax is
this:

else if (another_condition_to_test) {

}

Change your code to this, to see how else if works:

<?PHP

$kitten_image = 1;
$church_image = 0;

if ($kitten_image == 1) {

print (“<IMG SRC =images/kitten.jpg>”);

}
else if ($church_image == 1) {

print (“<IMG SRC =images/church.jpg>”);

}
else {

print (“No value of 1 detected”);

}

?>

Here’s we’re just testing to see which of our variables holds a value
of 1. But notice the “else if” lines (and that there’s a space
between else and if):

else if ($church_image == 1) {

print (“<IMG SRC =images/church.jpg>”);

}

What you’re saying is “If the previous if statement isn’t true,
then try this one.” PHP will then try to evaluate the new condition. If
it’s true (the $church_image variable holds a value of 1), then
the code between the new curly brackets gets executes. If it’s false (the
$church_image variable does NOT holds a value of 1), then the line of
code will be ignored, and PHP will move on.

To catch any other eventualities, we have an “else” part at the end.
Notice that all parts (if, else if, and else) are neatly sectioned of with pairs
of curly brackets:

if ($kitten_image == 1) {

}

else if ($church_image == 1) {

}

else {

}

You can add as many else if parts as you like, one for each condition that
you want to test. But change your two variables from this:

$kitten_image = 1;
$church_image = 0;

to this:

$kitten_image = 0;
$church_image = 0;

Then run your code again. What do you expect to happen?

As a nice example of if statements, there is a file called “selectPicture.php”
in the files that you downloaded. It’s
in the scripts folder. Copy this to your own www (root) folder. As long
as you have all the images mentioned in the script, they should display. But
examine the code for the script (ignore the HTML form tags for now). What it
does is to display an image, based on what the user selected from a drop down
list. If statements are being used to test what is inside of a single variable.

Don’t worry too much about the rest of the code: concentrate on the if
statements. All we’re doing is testing what is inside of the variable called
$picture. We’re then displaying the image that corresponds to the
word held in the variable.

 

Since you will be using if statements a heck of lot in your coding career,
it’s essential that you have a good grasp of how to use them. To help you
along, there’s some more about Conditional logic in the next section!

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