Classes within Classes

Created June 14, 2019 14:24

Hi all,

I have a class thus:

[code]

class Webpage
{
   public $system_licence = false;

   public function __construct() {
        $system_licence = new Licence;
        $system_licence->is_valid = true;
   }
}

class Licence {

    public $id = false;
    public $start_datetime = false;
    public $end_datetime = false;
    public $days_remaining = false;
    public $is_valid = false;
}

[/code]

In my main page I create an instance of the Webpage class thus:

[code]

$this_page = new Webpage;

if($this_page->system_licence->is_valid == true) {

// do something

}

[/code]

However PHP says that is_valid is being dynamically created, even though it is a property of the Licence object which is created within the Webpage object.

Why does it do this please?

5 comments

Eugene Morozov

Created June 14, 2019 22:09

In the Webpage constructor, you create a local variable that goes nowhere instead of assigning a value to the field.

Here's what the code is supposed to look like:

class Webpage
{
   public $system_licence = false;

   public function __construct() {
        $this->system_licence = new Licence;
        $this->system_licence->is_valid = true;
   }
}

Chris

Created June 15, 2019 10:04

Sorry - my mistake. I do include the $this-> elements in the constructor but whilst trying to represent it here for you I missed it out.

So, my code does read as you suggest, but the problem still occurs.

Andriy Bazanov

Created June 15, 2019 10:40

@Chris

You would need to show the real / test code that shows the issue (that we can copy-paste and see the issue locally), otherwise it's "guess where I have made a mistake / how my real code looks like" ... as your current example shows no such issues:

Chris

Created June 15, 2019 11:07

Index.php is at: https://pastebin.com/Tr3D9aLX

Webpage.php is at: https://pastebin.com/sT8BsJpK

You already have the total content of Licence.php i.e.:

<?php
    class Licence
    {
        public $id = false;
        public $start_datetime = false;
        public $end_datetime = false;
        public $days_remaining = false;
        public $is_valid = false;
    }


You will note that in Webpage.php the $system_licence variable is defined at line 32, created at line 146, and the is_valid value is set at line 153 or 154.

The error concerned is at line 29 of Index where is queries the is_valid as being wrong:

https://1drv.ms/u/s!AoOAUeu7fqnZh_Ni9_sEXT-8mKvh8g

Thanks in advance.

Andriy Bazanov

Created June 15, 2019 12:31

@Chris

Thanks for the files.

The reason is simple: due to the way how you declared $system_licence and assignment happens in another method (not in constructor) IDE treats system_license as boolean variable (due to public $system_licence = false;) ... which obviously cannot have own fields.

Solution is very simple: use better declaration.

Either move "$this->system_licence = new Licence;" line into constructor (constructors have special treatment for field assignments .. and IDE will treat this field as bool OR Licence)
or use PHPDoc comment to tell IDE what type that variable is, like this:

/** @var Licence */
public $system_licence;

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