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8Polymorphism
As we explained before, polymorphism is the process of creating several objects from
specific base classes. For example, take a look at the following case in point. We need
the three classes that we created earlier in this chapter, Emailer, ExtendedEmailer
and HtmlEmailer. Let's take a look at the following code.
include("class.emailer.php");
include("class.extendedemailer.php");
include("class.htmlemailer.php");
$emailer = new Emailer("hasin@somewherein.net");
$extendedemailer = new ExtendedEmailer();
$htmlemailer = new HtmlEmailer("hasin@somewherein.net");
if ($extendedemailer instanceof emailer )
echo "Extended Emailer is Derived from Emailer.
";
if ($htmlemailer instanceof emailer )
echo "HTML Emailer is also Derived from Emailer.
";
if ($emailer instanceof htmlEmailer )
echo "Emailer is Derived from HTMLEmailer.
";
if ($htmlemailer instanceof extendedEmailer )
echo "HTML Emailer is Derived from Emailer.
";
?>
If you execute the script above, you will find the following output:
Extended Emailer is Derived from Emailer.
HTML Emailer is also Derived from Emailer.
Kick-Starting OOP
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This is an example of polymorphism.
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