richiamare funzioni da classe figlia

[whisher]

<?php 
class Upload { 

    var $folders = null; 
    var $dir = null; 
     //costruttore 
    function Upload( $folders, $dir){ 
         $this->folders= $folders; 
        $this->dir= $dir;    
    } 
    //funzione 
       function checkSize($option){ 
        echo $this->folders;
        echo $this->dir;
           echo $option;   
    } 
     
}
class UploadIMG extends Upload { 

    var $alb_imgwidth = null; 
    var $alb_imgquality = null; 
       

      //costruttore 
    function UploadIMG( $folders, $dir, $alb_imgwidth, $alb_imgquality){          
            $this->alb_imgwidth = $alb_imgwidth; 
              $this->alb_imgquality = $alb_imgquality; 
            
            //richiamo classe madre per istanziare le proprietà ereditate 
            parent::Upload($folders,$dir); 
       }     
       
       function pinco ($option){ 
           $this->checkSize($option); 
          
       } 
}
$o= new UploadIMG('uno','due','','');  
$o->pinco('tre');
?>

Non vedo niente di sbagliato.