Overloading
Overloading in PHP provides means to dynamically "create" properties and methods. These dynamic entities are processed via magic methods one can establish in a class for various action types.
The overloading methods are invoked when interacting with properties or methods that have not been declared or are not visible in the current scope. The rest of this section will use the terms "inaccessible properties" and "inaccessible methods" to refer to this combination of declaration and visibility.
All overloading methods must be defined as public.
Note: None of the arguments of these magic methods can be passed by reference. Note: PHP's interpretation of "overloading" is different than most object oriented languages. Overloading traditionally provides the ability to have multiple methods with the same name but different quantities and types of arguments.
Changelog
Version | Description |
|---|---|
5.3.0 | Added __callStatic(). Added warning to enforce public visibility and non-static declaration. |
5.1.0 | Added __isset() and __unset(). Added support for __get() for overloading of private properties. |
5.0.0 | Added __get(). |
Property overloading
public void __set ( string $name , mixed $value )public mixed __get ( string $name )public bool __isset ( string $name )public void __unset ( string $name )__set() is run when writing data to inaccessible properties.
__get() is utilized for reading data from inaccessible properties.
__isset() is triggered by calling isset() or empty() on inaccessible properties.
__unset() is invoked when unset() is used on inaccessible properties.
The $name argument is the name of the property being interacted with. The __set() method's $value argument specifies the value the $name'ed property should be set to.
Property overloading only works in object context. These magic methods will not be triggered in static context. Therefore these methods should not be declared static. As of PHP 5.3.0, a warning is issued if one of the magic overloading methods is declared static.
Note: The return value of __set() is ignored because of the way PHP processes the assignment operator. Similarly, __get() is never called when chaining assignments together like this: $a = $obj->b = 8;
Example #1 Overloading properties via the __get(), __set(), __isset() and __unset() methods
<?php
class?PropertyTest
{
????/**??Location?for?overloaded?data.??*/
????private?$data?=?array();
????/**??Overloading?not?used?on?declared?properties.??*/
????public?$declared?=?1;
????/**??Overloading?only?used?on?this?when?accessed?outside?the?class.??*/
????private?$hidden?=?2;
????public?function?__set($name,?$value)
????{
????????echo?"Setting?'$name'?to?'$value'\n";
????????$this->data[$name]?=?$value;
????}
????public?function?__get($name)
????{
????????echo?"Getting?'$name'\n";
????????if?(array_key_exists($name,?$this->data))?{
????????????return?$this->data[$name];
????????}
????????$trace?=?debug_backtrace();
????????trigger_error(
????????????'Undefined?property?via?__get():?'?.?$name?.
????????????'?in?'?.?$trace[0]['file']?.
????????????'?on?line?'?.?$trace[0]['line'],
????????????E_USER_NOTICE);
????????return?null;
????}
????/**??As?of?PHP?5.1.0??*/
????public?function?__isset($name)
????{
????????echo?"Is?'$name'?set?\n";
????????return?isset($this->data[$name]);
????}
????/**??As?of?PHP?5.1.0??*/
????public?function?__unset($name)
????{
????????echo?"Unsetting?'$name'\n";
????????unset($this->data[$name]);
????}
????/**??Not?a?magic?method,?just?here?for?example.??*/
????public?function?getHidden()
????{
????????return?$this->hidden;
????}
}
echo?"<pre>\n";
$obj?=?new?PropertyTest;
$obj->a?=?1;
echo?$obj->a?.?"\n\n";
var_dump(isset($obj->a));
unset($obj->a);
var_dump(isset($obj->a));
echo?"\n";
echo?$obj->declared?.?"\n\n";
echo?"Let's?experiment?with?the?private?property?named?'hidden':\n";
echo?"Privates?are?visible?inside?the?class,?so?__get()?not?used...\n";
echo?$obj->getHidden()?.?"\n";
echo?"Privates?not?visible?outside?of?class,?so?__get()?is?used...\n";
echo?$obj->hidden?.?"\n";
?>The above example will output:
Setting 'a' to '1'
Getting 'a'
1
Is 'a' set?
bool(true)
Unsetting 'a'
Is 'a' set?
bool(false)
1
Let's experiment with the private property named 'hidden':
Privates are visible inside the class, so __get() not used...
2
Privates not visible outside of class, so __get() is used...
Getting 'hidden'
Notice: Undefined property via __get(): hidden in <file> on line 70 in <file> on line 29Method overloading
public mixed __call ( string $name , array $arguments )public static mixed __callStatic ( string $name , array $arguments )__call() is triggered when invoking inaccessible methods in an object context.
__callStatic() is triggered when invoking inaccessible methods in a static context.
The $name argument is the name of the method being called. The $arguments argument is an enumerated array containing the parameters passed to the $name'ed method.
Example #2 Overloading methods via the __call() and __callStatic() methods
<?php
class?MethodTest
{
????public?function?__call($name,?$arguments)
????{
????????//?Note:?value?of?$name?is?case?sensitive.
????????echo?"Calling?object?method?'$name'?"
?????????????.?implode(',?',?$arguments).?"\n";
????}
????/**??As?of?PHP?5.3.0??*/
????public?static?function?__callStatic($name,?$arguments)
????{
????????//?Note:?value?of?$name?is?case?sensitive.
????????echo?"Calling?static?method?'$name'?"
?????????????.?implode(',?',?$arguments).?"\n";
????}
}
$obj?=?new?MethodTest;
$obj->runTest('in?object?context');
MethodTest::runTest('in?static?context');??//?As?of?PHP?5.3.0
?>The above example will output:
Calling object method 'runTest' in object context
Calling static method 'runTest' in static context← Anonymous classes
Object Iteration →
? 1997–2017 The PHP Documentation GroupLicensed under the Creative Commons Attribution License v3.0 or later.
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