Home » Php » class – PHP – extended __construct

class – PHP – extended __construct

Posted by: admin April 23, 2020 Leave a comment

Questions:

I was wondering if you could help me out..

I have two classes, one extends the other.. Class B will be extended by various different objects and used for common database interactions.. Now I would like class B to handle its connect and disconnects without direction from class A or any external input..

The problem from what I understand is that an extended class won’t automatically run its __construct function.. Is there a way around this?

Thanks in advance..

class a extends b
{
   public function __construct()
   {
   }   

   public function validateStuff()
   {
      $this->insert_record();
   }
}

class b
{
   public function __construct()
   {
      $this->connect();
   }

   protected function connect()
   {
      return true;
   }

   public function insert_record()
   {
      return true;
   }
}
How to&Answers:

The parent __construct() method defined in class b will run automatically if you instantiate child class a, unless there is a __construct() method defined in class a.

class a extends b { 
} 

class b { 
   public function __construct() 
   { 
      echo 'In B Constructor'; 
   } 
} 

$x = new a();

If a __construct() method is defined in class a, then this overrides the use of the __construct() method in class b…. it will run instead of the class b __construct() method

class a extends b { 
   public function __construct() 
   { 
      echo 'In A Constructor'; 
   } 
} 

class b { 
   public function __construct() 
   { 
      echo 'In B Constructor'; 
   } 
} 

$x = new a();

So if your child class has a __construct() method defined, then you need to explicitly call the constructor for the parent if you want to execute that as well.

class a extends b { 
   public function __construct() 
   { 
      parent::__construct();
      echo 'In A Constructor'; 
   } 
} 

class b { 
   public function __construct() 
   { 
      echo 'In B Constructor'; 
   } 
} 

$x = new a();

Answer:

I’m not sure I fully understand what you are asking, but you can call the parents construct method from the child’s constructor

parent::__construct();

That’s the only option I know of.

Answer:

Call parent::__construct() in a::__construct():

class a extends b
{
   public function __construct()
   {
       parent::__construct();
   }   

   public function validateStuff()
   {
      $this->insert_record();
   }
}

You can omit a’s constructor altogether if you’re not doing any a-specific stuff.