Function call through class recursion?

Question

Within my code, I have two classes- the first "Foo" initiates the second "Bar"... what I want to do is find some method of using the functions and variables from the parent.

class Bar {
    function __construct() {
        /* 
         * From within this function, how do I access either the returnName() function
         * OR the $this -> name variable from the class above this?
         * The result being:
         */
        $this -> name = parent::returnName();
        $this -> else = parent -> name;
    }
}

class Foo {
    function __construct() {
        $this -> name = 'Fred';
        $this -> var = new Bar();
    }

    function returnName() {
        return $this -> name;
    }
}

$salad = new Foo();

I realise the syntax of "parent" refers to either an implement or extends, but is it possible to use this kind of method?

Daan · Accepted Answer · 2016-03-17 12:53:50Z

3

You can inject $this (the Foo class) in the constructor of Bar

<?php
class Bar {
    function __construct($fooClass) {
        /* 
         * From within this function, how do I access either the returnName() function
         * OR the $this -> name variable from the class above this?
         * The result being:
         */
        $this -> name = $fooClass->returnName();
        $this -> else = $fooClass -> name;
    }
}

class Foo {
    function __construct() {
        $this -> name = 'Fred';
        $this -> var = new Bar($this);
    }

    function returnName() {
        return $this -> name;
    }
}

$salad = new Foo();

answered Mar 17, 2016 at 12:53

Daan

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6 Comments

lukesrw Over a year ago

Thanks, I knew I would do this- though I didn't want to pass as an argument unless I absolutely had to.

Tanuel Mategi Over a year ago

debug_backtrace() Take a look at my answer for an example with your classes ;)

lukesrw Over a year ago

For Daan, the Bar class is now trying to use a function from Foo, "Call to undefined method Bar::returnName()". Solution to this?

Daan Over a year ago

You're calling returnName() statically (::). Call it like this $fooClass->returnName();

lukesrw Over a year ago

I'm not using ::, I am using $this -> returnName(); How would I ensure that it always uses Foo class, no matter whether it is called by Foo OR Bar.

|

Tanuel Mategi · Accepted Answer · 2016-03-17 13:10:53Z

0

Handle with care

This is not a 100% clean solution, but will work. Your code should be well documented to avoid future confusion.

There is a very cool function called debug_backtrace()

It gives you information about all the calls that were made to get to this function, including the filename, the line it was called, the called function, the class and object name and the arguments.

Here is how you could use it:

class Bar {
    function __construct() {

        //get backtrace info
        $trace = debug_backtrace();
        //get the object from the function that called class
        //and call the returnName() function
        $this->name = $trace[1]['object']->returnName();
        echo $this->name;

        //want more info about backtrace? use print_r($trace);
    }
}

class Foo {
    function __construct() {
        $this -> name = 'Fred';
        $this -> var = new Bar();
    }

    function returnName() {
        return $this -> name;
    }
}

$salad = new Foo();

Result:

Fred

edited Mar 17, 2016 at 13:10

answered Mar 17, 2016 at 12:57

Tanuel Mategi

1,2836 silver badges14 bronze badges

3 Comments

lukesrw Over a year ago

The function part of my question is currently the most important answer, though this seems like it might be best for variables- am I right in thinking this would be slower than using $this as an argument when calling Bar?

Tanuel Mategi Over a year ago

You can try a benchmark, but it works pretty fast. I use debug_backtrace() in a few of my applications and the whole page doesnt take more than 0.08 seconds to load. edit: also take a look here: PHP debug_backtrace in production code to get information about calling method?

lukesrw Over a year ago

Thanks! Still looking into getting functions to work, I'll be sure to use this if needed.

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