Appending values from a child class to parent class

Question

I have a file eg class.php with following code:

//class.php 
class main_class { 

public $output;

public function print_me ( $msg ){
$this->output .= $msg.'\r\n' ;
}

//….
//….
//more functions
// some of them using this->print_me 

} 

class sub_class extends main_class { 

function verification (){ 
this->print_me ( 'Log: while verification' );
}

}
//class.php ends

I need to initiate main_class in main.php file, code of main.php file is as follows

 //main.php 
require 'class.php';
    $main_class = new main_class();
    //and need to append values into output variables
$main_class->print_me ( 'Log: from main.php ' );
//but before echoing , I need to initiate sub class as follows:
//$sub_class = new $sub_class();
//though I do not need to append/ values using $sub_class instance , 
//I need to append value from within the class itself at last I can print output variable e.g. 
echo $main_class->output;

later I knew , class sub_class code is wrong , so changed from

function verification (){ 
this->print_me ( 'Log: while verification' );
}

to

function verification (){ 
parent::print_me ( 'Log: while verification' );
}

but this does not work either , I fail to append values into main_class's output variable so that i can print at last all of logs

Answer 1

You should have to use like this

$sub_class = new sub_class();
$sub_class->verification ( 'Log: from main.php 1 ' );
$sub_class->verification ( 'Log: from main.php 2 ' );
echo $sub_class->output;

just use the subclass object to get the log.

main class object could not return you any thing due to polymorphism.