在子类中访问父方法的正确方法

Question

I have a ChildClass that extends to a ParentClass . The ParentClass has a constructor that takes two arguments __construct('value2', ParentClass::COMMON) . HOwever I am trying to call the inherited newSelect() method from within the child class. So far it has not been succesfull. How would I call NewSelect() from the ChildClass ? Also is it possible even though the ParentClass has a constructor that takes two parameters?

Parent

class ParentClass {    

const COMMON = 'common';

protected $db;

protected $common = false;

protected $quotes = array(
'Common' => array('"', '"'),
'Value2' => array('`', '`'),
'Value3' => array('`', '`'),
'Value4' => array('`', '`'),
);

protected $quote_name_prefix;

protected $quote_name_suffix;

   public function __construct($db, $common = null) {
    $this->db = ucfirst(strtolower($db));
    $this->common = ($common === self::COMMON);
    $this->quote_name_prefix = $this->quotes[$this->db][0];
    $this->quote_name_suffix = $this->quotes[$this->db][1];
   }

 public function newSelect() {
    return $this->newInstance('Select');
 }

 protected function newInstance($query) {
    //Some more code,  not relevant to example
 }


}

Child

class ChildClass extends ParentClass {    



    public function __construct() {

    }

    // Call the inherited method

    private $_select = Parent::newSelect();

    // Do something with it

}

Answer 1

// you can't do this

private $_select = Parent::newSelect();

// try this

private $_select;

public function construct($value, $common)
{
    Parent::__construct($value, $common);
    $this->_select = $this->newSelect();
}

// and

$obj = new ChildClass('Value2', ParentClass::COMMON); //  ParentClass::COMMON - not sure why you would do this
$select = $obj->newSelect(); // this is being called in constructor, why call it again

and to be honest, I don't even know what you're trying to do but everything about it looks wrong too!