php-doc-en/reference/overload/examples.xml

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<appendix xml:id="overload.examples" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 &reftitle.examples;
 <section xml:id="overload.examples.basic">
  <para>
   Some simple examples on using the <function>overload</function>
   function:
   <example>
    <title>Overloading a PHP class</title>
    <programlisting role="php">
<![CDATA[
<?php

class OO {
   var $a = 111;
   var $elem = array('b' => 9, 'c' => 42);

   // Callback method for getting a property
   function __get($prop_name, &$prop_value) 
   {
       if (isset($this->elem[$prop_name])) {
           $prop_value = $this->elem[$prop_name];
           return true;
       } else {
           return false;
       }
   }

   // Callback method for setting a property
   function __set($prop_name, $prop_value) 
   {
       $this->elem[$prop_name] = $prop_value;
       return true;
   }
}

// Here we overload the OO object
overload('OO');

$o = new OO;
echo "\$o->a: $o->a\n"; // print: $o->a: 111
echo "\$o->b: $o->b\n"; // print: $o->b: 9
echo "\$o->c: $o->c\n"; // print: $o->c: 42
echo "\$o->d: $o->d\n"; // print: $o->d:

// add a new item to the $elem array in OO
$o->x = 56; 

// instantiate stdclass (it is built-in PHP 4)
// $val is not overloaded!
$val = new stdclass;
$val->prop = 555;

// Set "a" to be an array with the $val object in it
// But __set() will put this in the $elem array
$o->a = array($val);
var_dump($o->a[0]->prop);

?>
]]>
    </programlisting>
   </example>
  </para>
 </section>
</appendix>

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