Unable to call a class in php
===

               <?php
            try{
           
              $test = new TestAccessModifiers("2345","xyz", 
  

                                "vfd","a0001","99","67"); /*invoking the class*/
         
                  var_dump($test->calculate());
        }
        catch(Exception $e){
            
            echo $e->getMessage();
        }
        ?>
   

class TestAccessModifiers {
   
    
     function TestAccessModifiers($user_p,$user_fn,$user_ln,$user_id,$marks1,$marks2) {
         echo "hello1";
        $this->user_phone=$user_p;
        $this->user_fname=$user_fn;
        $this->user_lname=$user_ln;
        $this->user_id=$user_id;
        $this->marks1=$marks1;
        $this->marks2=$marks2;
        
       
        echo $this->marks1;
    }
    private  $additional_marks = 10;
    public static function calculate(){
        
        
        return $this->marks1+$this->marks2+$this->getAdditionalmarks();
        
    }
    
    public function getAdditionalmarks(){
        
        return $this->additional_marks;
    }
    
        
}

 
   
 Above is the simple code i am trying to run... but i am unable to call TestAccessModifiers 
I have tried using _constructor too 
 ...please help...thanks