Question

How can I call a method of an object passed as a parameter in PHP?

This is the first class defined in thefirstclass.php

class TheFirstClass {

    private $_city='Madrid';

    public function city() {
        return $_city
    }   
}

This is the second class defined in thesecondclass.php

class TheSecondClass {

    public function myMethod($firstClassObject) {

        echo "City: " . $firstClassObject->city(); // <- Why This method doesn´t work?      

    }
}

And finally, this is
include_once “class/thefirstclass.php”;
include_once “class/thesecondclass.php”;

$firstClassObject = new TheFirstClass();
$secondClassObject = new TheSecondClass();

$secondClassObject->myMethod($firstClassObject);

Answer 1

The problem doesn’t lie in the call to TheFirstClass::city within TheSecondClass::myMethod, but rather that TheFirstClass::city returns a local variable ($_city) rather than an instance variable ($this->_city). Unlike in languages such as C++, in PHP instance variables must always be accessed through an object, even in methods.

This is the working code:

class TheFirstClass {
    private $_city = "a";

    public function city() {
        return $this->_city;
    }   
}

class TheSecondClass {
    public function myMethod($firstClassObject) {
        echo "City: " . $firstClassObject->city(); // <- Why This method doesn´t work?
    }
}

$test = new TheFirstClass();
$test2 = new TheSecondClass();
$test2->myMethod($test);