Reload_PHP Tutorial

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PHP4 already has overloading syntax to establish mapping to external object models, just like Java and COM. PHP5 brings powerful object-oriented overloading, allowing programmers to create custom behaviors to access properties and call method.

Overloading can be performed through several special methods: __get, __set, and __call. When the Zend engine tries to access a member and cannot find it, PHP will call these methods.

In Example 6.14, __get and __set replace all accesses to the attribute variable array. If necessary, you can implement any type of filtering you want. For example, the script can disable setting attribute values, start with a certain prefix or include A value of a certain type.

The __call method explains how you call an undefined method. When you call an undefined method, the method name and the parameters received by the method will be passed to the __call method, and PHP returns the value of __call to the undefined method.

Listing 6.14 User-level overloading


class Overloader
{
private $properties = array();

function __get($property_name)
{
if(isset($this->properties[$property_name]))
{
return($this->properties[$property_name]);
}
else
{
return(NULL);
}
}

function __set($property_name, $value)
{
$this->properties[$property_name] = $value;
}

function __call($function_name, $args)
{
print("Invoking $function_name()
n");
print("Arguments: ");
print_r($args);

return(TRUE);
}
}
$o = new Overloader();

//invoke __set() assigns a value to a non-existent attribute variable and activates __set()
$o->dynaProp = "Dynamic Content";

//invoke __get() activates __get()
print($o->dynaProp . "
n");

//invoke __call() activate __call()
$o->dynaMethod("Leon", "Zeev");
?>

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