PHP Class Magic Methods
Description
Whenever you see a method name start with a double underscore, it is a "magic"
method.
PHP reserves all methods starting with __ as magic.
Magic method list
PHP allows you to create three " magic " methods that you can use to intercept property and method accesses:
- __get() is called whenever the calling code attempts to read an invisible property of the object
- __set() is called whenever the calling code attempts to write to an invisible property of the object
- __call() is called whenever the calling code attempts to call an invisible method of the object
visible refers to non-existing property or method or private or protected the property or method.
__get()
__get() specifies what to do when loading an unknown property.
For example:
<?PHP/*w ww . jav a2s. com*/
class Book {
public $Name;
public function __get($var) {
print "Attempted to retrieve $var and failed...\n";
}
}
$aBook = new Book;
print $aBook->Price;
?>
Overloading Property Accesses with __get()
<?PHP/*from www . j a v a2 s . com*/
class Car {
public function __get( $propertyName ) {
echo "The value of '$propertyName' was requested < br / > ";
return "blue";
}
}
$car = new Car;
$x = $car->color;
echo "The car's color is $x \n";
?>
The code above generates the following result.
__set()
Use __set() method to catch an attempt to set an invisible property to a value, use needs two parameters: the property name and the value to set it to.
It does not need to return a value:
public function __set( $propertyName, $propertyValue ) {
// (do whatever needs to be done to set the property value)
}
The __set() magic method is called when setting an undefined property.
<?PHP//w ww .ja v a 2 s . c o m
class Book {
public function __set($var, $val) {
print("UPDATE $var = '$val';");
}
}
$book = new Book();
$book ->Price= 1.2;
?>
The code above generates the following result.
__call()
Use __call() to handle calls to nonexistent methods of a class. The method should then return a value (if any) back to the calling code:
public function __call( $methodName, $arguments ) {
// (do stuff here)
return $returnVal;
}
The __call() magic method is called when calling a missing method. Here's an example of __call() in action:
<?PHP/*from ww w . j av a 2 s . c o m*/
class Book {
public function __call($function, $args) {
$args = implode(', ', $args);
print "Call to $function() with args '$args' failed!\n";
}
}
$aBook = new Book;
$aBook->nonExistingMethod("foo", "bar", "baz");
?>
The code above generates the following result.
__toString()
__toString() allows you to set a string value for the object.
<?PHP/* w w w . j a v a 2s . co m*/
class Cat {
public function __toString() {
return "This is a cat\n";
}
}
$c = new Cat;
print $c;
?>
The code above generates the following result.
