Using static function in extended class in PHP

Question

I have an abstract class that has a method which uses a static function. This static function is defined in sub-classes and is different for each sub-class. Which sub-class will be used to create object is determined in the script. See super simplified code below:

abstract class fooClass implements iFooClass {    
    function getBar(){
        $bar = self::getSomething();
        return $bar;
    }        
}

interface iFooClass{
    static function getSomething();
}

class fooSubClass_A extends fooClass {
    static function getSomething() {
        //do something;
        //return something;
    }
}

class fooSubClass_B extends fooClass {
    static function getSomething() {
        //do something else;
        //return something else;
    }
}

$foo = New fooSubClass_A;
$bar = $foo->getBar();

This code gives me this error:

Fatal error: Cannot call abstract method iFooClass::getSomething() in C:\wamp\www\Classes\fooClass.php on line 12

I thought since the sub-classes have access to super-classes method getBar it would be called from the sub-class and thus have access to its static function. Apparently not. Is there a way to redo this to make it work?

David Demetradze · Accepted Answer · 2015-03-15 10:12:08Z

2

I think at first you should implement "getSomething" method from "iFooClass" interface in "fooClass" because all interface functions must be implemented in child class, that's the basic rule of interfaces. Only after that you can include this function into another class method.

Edit: Abstract classes have ability not to implement all interface methods, if they are implemented in it's subclasses.

Edit2 When you call method with Self keyword, it calls method from class where "SELF" actually exists and not from class object from which we are calling method. That's why self::method() should be changed with static::method()

edited Mar 15, 2015 at 10:12

answered Mar 15, 2015 at 9:23

David Demetradze

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4 Comments

user2395238 Over a year ago

but fooClass is abstract class that will never be really instantiated and getSomething is a static method that is only defined in children and is slightly different for each child. What implementation should I put in the abstract class fooClass? just an empty method static function getSomething(){}?

David Demetradze Over a year ago

static function getSomething() { echo "All"; } i added this in fooClass and worked fine :).

user2395238 Over a year ago

is it calling fooSubClass_A static method? because that's the static method I want to be calling in the example above.

David Demetradze Over a year ago

I solved this problem. You are using self in foosubClass wich means that when you call it, you call method from class where it actually exists and not from class your object is from. Change self::getbar() to static::getbar()

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