examples.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->

<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, 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>Class Definitions</title>
   <para><varname>Vegetable</varname></para>
   <programlisting role="php">
<![CDATA[
<?php

class Vegetable {
    public $edible;

    public $color;

    public function __construct($edible, $color = "green")
    {
        $this->edible = $edible;
        $this->color = $color;
    }

    public function isEdible()
    {
        return $this->edible;
    }

    public function getColor()
    {
        return $this->color;
    }
}

?>
]]>
   </programlisting>
   <para><varname>Spinach</varname></para>
   <programlisting role="php">
<![CDATA[
<?php

class Spinach extends Vegetable {
    public $cooked = false;

    public function __construct()
    {
        parent::__construct(true, "green");
    }

    public function cook()
    {
        $this->cooked = true;
    }

    public function isCooked()
    {
        return $this->cooked;
    }
}

?>
]]>
   </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[
<?php

// register autoloader to load classes
spl_autoload_register();

function printProperties($obj)
{
    foreach (get_object_vars($obj) as $prop => $val) {
        echo "\t$prop = $val\n";
    }
}

function printMethods($obj)
{
    $arr = get_class_methods(get_class($obj));
    foreach ($arr as $method) {
        echo "\tfunction $method()\n";
    }
}

function objectBelongsTo($obj, $class)
{
    if (is_subclass_of($obj, $class)) {
        echo "Object belongs to class " . get_class($obj);
        echo ", a subclass of $class\n";
    } else {
        echo "Object 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";
printProperties($veggie);

// and leafy methods
echo "\nleafy: Methods\n";
printMethods($leafy);

echo "\nParentage:\n";
objectBelongsTo($leafy, Spinach::class);
objectBelongsTo($leafy, Vegetable::class);

?>
]]>
   </programlisting>
   &examples.outputs;
   <screen>
<![CDATA[
veggie: CLASS Vegetable
leafy: CLASS Spinach, PARENT Vegetable

veggie: Properties
        edible = 1
        color = blue

leafy: Methods
        function __construct()
        function cook()
        function isCooked()
        function isEdible()
        function getColor()

Parentage:
Object does not belong to a subclass of Spinach
Object belongs to class Spinach, a subclass of Vegetable
]]>
   </screen>
   <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>.
   </para>
  </example>
 </para>
</appendix>

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