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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<appendix xml:id="classobj.examples">
&reftitle.examples;
<para>
In this example, we first define a base class and an extension
of the class. The base class describes a general vegetable,
whether it is edible or not and what is its color. The subclass
<varname>Spinach</varname> adds a method to cook it and another to
find out if it is cooked.
</para>
<para>
<example>
<title>classes.inc</title>
<programlisting role="php">
<![CDATA[
<?php
// base class with member properties and methods
class Vegetable {
var $edible;
var $color;
function Vegetable($edible, $color="green")
{
$this->edible = $edible;
$this->color = $color;
}
function is_edible()
{
return $this->edible;
}
function what_color()
{
return $this->color;
}
} // end of class Vegetable
// extends the base class
class Spinach extends Vegetable {
var $cooked = false;
function Spinach()
{
$this->Vegetable(true, "green");
}
function cook_it()
{
$this->cooked = true;
}
function is_cooked()
{
return $this->cooked;
}
} // end of class Spinach
?>
]]>
</programlisting>
</example>
</para>
<para>
We then instantiate 2 objects from these classes and print out
information about them, including their class parentage.
We also define some utility functions, mainly to have a nice printout
of the variables.
</para>
<para>
<example>
<title>test_script.php</title>
<programlisting role="php">
<![CDATA[
<pre>
<?php
include "classes.inc";
// utility functions
function print_vars($obj)
{
foreach (get_object_vars($obj) as $prop => $val) {
echo "\t$prop = $val\n";
}
}
function print_methods($obj)
{
$arr = get_class_methods(get_class($obj));
foreach ($arr as $method) {
echo "\tfunction $method()\n";
}
}
function class_parentage($obj, $class)
{
if (is_subclass_of($GLOBALS[$obj], $class)) {
echo "Object $obj belongs to class " . get_class($$obj);
echo " a subclass of $class\n";
} else {
echo "Object $obj does not belong to a subclass of $class\n";
}
}
// instantiate 2 objects
$veggie = new Vegetable(true, "blue");
$leafy = new Spinach();
// print out information about objects
echo "veggie: CLASS " . get_class($veggie) . "\n";
echo "leafy: CLASS " . get_class($leafy);
echo ", PARENT " . get_parent_class($leafy) . "\n";
// show veggie properties
echo "\nveggie: Properties\n";
print_vars($veggie);
// and leafy methods
echo "\nleafy: Methods\n";
print_methods($leafy);
echo "\nParentage:\n";
class_parentage("leafy", "Spinach");
class_parentage("leafy", "Vegetable");
?>
</pre>
]]>
</programlisting>
<para>
One important thing to note in the example above is that
the object <varname>$leafy</varname> is an instance of the class
<classname>Spinach</classname> which is a subclass of
<classname>Vegetable</classname>,
therefore the last part of the script above will output:
</para>
<screen>
<![CDATA[
[...]
Parentage:
Object leafy does not belong to a subclass of Spinach
Object leafy belongs to class spinach a subclass of Vegetable
]]>
</screen>
</example>
</para>
</appendix>
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