Code confusion while extending PHP exception class -

this question related extending php exception class , there many similar questions 1 different.

i trying extend php exception class can add values exception message. below code.

class om_exception extends exception {      public function __construct($message, $code = 0, exception $previous = null) {         $message = $this->_getmessage($message);         parent::__construct($message, $code, $previous);     }      protected function _getmessage($message) {         $exception = '<br />';         $exception .= '<b>exception  => </b>'.$message.'<br />';         $exception .= '<b>class => </b>'.get_called_class().'<br />';         $exception .= '<b>error line => </b>'.$this->getline().'<br />';         $exception .= '<b>error file => </b>'.$this->getfile().'<br />';         return $exception;     }  } 

this works fine. , problem.

since calling functions getline() , getfile() of parent class before calling constructor shouldn't return blank values? if not error?

but works fine , output described below.

exception => hello.. class => om_controller_exception error line => 30 error file => c:\users\jay\projects\order-manager\application\modules\default\controllers\logincontroller.php  

can please me understand why behavior? how can use class methods before initializing class?

the constructor called on newly created object, object , it's properties , methods exists when constructor called. example should make pretty clear:

<?php  class testparent {     protected $protectedstuff = 1;     public function __construct($intnumber) {         $this->protectedstuff = $intnumber;     } } class testchild extends testparent {     public function __construct($intnumber) {         echo get_class() . '<br />'; // testchild         echo get_parent_class() . '<br />'; // testparent         $this->printstuff(); // 1         parent::__construct($intnumber);         $this->printstuff(); // 42     }     public function printstuff() {         echo '<br />the number now: ' . $this->protectedstuff;     } } $objchild = new testchild(42); 

result

testchild

testparent

the number now: 1

the number now: 42