Question

I have a problem with extending the mysqli_result class.

I am trying to extend the mysqli_result class with a custom class.
Here is my code:

class mysqli_result_extended extends mysqli_result {

  public function GetJSON() {
    blah blah...
    return $json;   
  }       
}

$db = new mysqli('localhost','root','*****','somedb');

$sql = 'SELECT * FROM students';

$result = $db->query($sql);

$result->getJSON(); //This is causing the trouble

When I run the above code, it gives an error:

Call to undefined method mysqli_result::getJSON() in ****.php on line **

What’s wrong with this code?

Answer 1

You’re getting the error because the $db->query($sql) returns a variable of type mysqli_result and not mysqli_result_extended. The mysqli_result class doesn’t have a method named getJSON.

So when you define a class B that extends class A, it doesn’t mean that all instances of the base class A magically become class B.