Static Keyword
This page describes the use of the static keyword to
define static methods and properties. static can also
be used to
define static variables
and for
late static bindings.
Please refer to those pages for information on those meanings of
static.
Declaring class properties or methods as static makes them accessible without needing an instantiation of the class. These can also be accessed statically within an instantiated class object.
Static methods
Because static methods are callable without an instance of the object created, the pseudo-variable $this is not available inside methods declared as static.
Calling non-static methods statically throws an Error.
Prior to PHP 8.0.0, calling non-static methods statically were deprecated, and
generated an E_DEPRECATED warning.
Example #1 Static method example
<?php
class Foo {
public static function aStaticMethod() {
// ...
}
}
Foo::aStaticMethod();
$classname = 'Foo';
$classname::aStaticMethod();
?>
Static properties
Static properties are accessed using the
Scope Resolution Operator
(::) and cannot be accessed through the object operator
(->).
It's possible to reference the class using a variable.
The variable's value cannot be a keyword (e.g. self,
parent and static).
Example #2 Static property example
<?php
class Foo
{
public static $my_static = 'foo';
public function staticValue() {
return self::$my_static;
}
}
class Bar extends Foo
{
public function fooStatic() {
return parent::$my_static;
}
}
print Foo::$my_static . "\n";
$foo = new Foo();
print $foo->staticValue() . "\n";
print $foo->my_static . "\n"; // Undefined "Property" my_static
print $foo::$my_static . "\n";
$classname = 'Foo';
print $classname::$my_static . "\n";
print Bar::$my_static . "\n";
$bar = new Bar();
print $bar->fooStatic() . "\n";
?>
Output of the above example in PHP 8 is similar to:
foo foo Notice: Accessing static property Foo::$my_static as non static in /in/V0Rvv on line 23 Warning: Undefined property: Foo::$my_static in /in/V0Rvv on line 23 foo foo foo foo
