Variable overloading issue in PHP

amber.long83 · 06-22-2009, 08:02 AM

Hi friends

Thanks for visiting my post.

I have a issue in object inheritance in php. I have two classes which extends other. There is one common variable name used in both the class. So it's creating a conflict while accessing the parent class variable. Let me explain this by example

PHP Code:

  // First Class
class a {
    public $email    =    "a@a.com";    
}

class b extends a {
    public $email    =    "b@b.com";    
}

$obj    =    new b();
echo    $obj->email;    // this will print b@b.com but i want to print a@a.com

Can anyone guide me?

CMartin · 06-23-2009, 10:33 AM

Quote:

Originally Posted by amber.long83

I have a issue in object inheritance in php. I have two classes which extends other. There is one common variable name used in both the class. So it's creating a conflict while accessing the parent class variable. Let me explain this by example

PHP Code:

  // First Class

class a {

    public $email    =    "a@a.com";    

}

 
class b extends a {

    public $email    =    "b@b.com";    

}

 
$obj    =    new b();

echo    $obj->email;    // this will print b@b.com but i want to print a@a.com

Can anyone guide me?

The way it's working is the expected way... because you are changing the parent's variable value in the subclass when you declare it.

If you really need to declare the email variable in the subclass, then you could set the email variable in the main class to private and have a function to return the email value from the main class:

PHP Code:

  class a {

    private $email = "a@a.com";    

    function parentEmail() {return $this->email;}

}

 
class b extends a {

    public $email = "b@b.com";    

}

 
$obj = new b();

echo $obj->email; // this will print b@b.com

echo $obj->parentEmail(); // this will print a@a.com

What I would do is to not declare the $email variable in the subclass as it's already declared in the parent class. Class b could use a constructor where you can optionally pass an $email value - if you pass the email value you set the $email variable. An alternative is to use a setter function for the email in the subclass without using a constructor - example:

PHP Code:

  // First Class

class a {

    public $email = "a@a.com";    

}

 
class b extends a {

    function setEmail($email){

            $this->email = $email;

      } 

}

 
$obj = new b();

echo $obj->email;    // this will print a@a.com

$obj->setEmail("b@b.com");

echo $obj->email;    // this will print b@b.com

Carlos

amber.long83 · 06-25-2009, 05:12 AM

thanks CMartin

your tips seems perfect. i was wrong.

hi titleless,
parent keyword will not work here. its only used for function not for variable.

06-22-2009, 08:02 AM	#1
amber.long83 Warrior Member Join Date: Jun 2009 Posts: 5 Thanks: 2 Thanked 0 Times in 0 Posts	Variable overloading issue in PHP Hi friends Thanks for visiting my post. I have a issue in object inheritance in php. I have two classes which extends other. There is one common variable name used in both the class. So it's creating a conflict while accessing the parent class variable. Let me explain this by example PHP Code: `// First Class class a { public $email = "a@a.com"; } class b extends a { public $email = "b@b.com"; } $obj = new b(); echo $obj->email; // this will print b@b.com but i want to print a@a.com` Can anyone guide me?
	Magento Developer

06-25-2009, 05:12 AM	#3
amber.long83 Warrior Member Join Date: Jun 2009 Posts: 5 Thanks: 2 Thanked 0 Times in 0 Posts	Re: Variable overloading issue in PHP thanks CMartin your tips seems perfect. i was wrong. hi titleless, parent keyword will not work here. its only used for function not for variable.
	Magento Developer