How to Call Functions of Child Classes from Parent Classes in PHP

In PHP, a common task is invoking functions defined in child classes from within parent classes. Consider the following example:

class whale
{
  public function __construct()
  {
    // some code here
  }

  public function myfunc()
  {
    // How do I call the "test" function of the fish class here?
  }
}

class fish extends whale
{
  public function __construct()
  {
    parent::__construct();
  }

  public function test()
  {
    echo "So you managed to call me !!";
  }
}

Solution

One solution is to utilize abstract classes, which define essential functions that must be implemented by inheriting classes. Here's a modified code:

abstract class whale
{
  public function __construct()
  {
    // some code here
  }

  public function myfunc()
  {
    $this->test();
  }

  abstract public function test();
}

class fish extends whale
{
  public function __construct()
  {
    parent::__construct();
  }

  public function test()
  {
    echo "So you managed to call me !!";
  }
}

$fish = new fish();
$fish->test();
$fish->myfunc();

With this modification, you can invoke the test function of the fish class from the myfunc function of the whale class by calling $this->test(). This approach ensures that child classes must implement the test function.