after creating an inheritance it outputs NULL value - php

Question

I want to have my inheritance but it outputs null. it was working but when I extends Patient to clinic it starts to output null. my teachers instruction was to have inheritance and I need help im still studying about this inheritance but its kind a complicated for me.
<?php
class Patient{
private $name;
private $age;
private $gender;
public function record($name, $age, $gender){
$this->name = $name;
$this->age = $age;
$this->gender = $gender;
}
public function getName(){
return $this->name;
}
public function getAge(){
return $this->age;
}
public function getGender(){
return $this->gender;
}
}
class Clinic extends Patient{
private $patients = [];
public function getPatients(){
return $this->patients;
}
public function assignPatient($name, $age, $gender){
$this->patients[] = new Patient($name, $age, $gender);
}
public function deletePatient($index){
unset($this->patients[$index]);
}
}
$clinic = new Clinic();
$clinic->assignPatient("Patrick star",18,"Male");
$clinic->assignPatient("SpongeBob Squarepants",17,"Male");
$clinic->assignPatient("Eugene Krab",28,"Male");
$clinic->deletePatient(1);
var_dump($clinic->getPatients());

Answer 1

A few things to change here. First, you called the function for a new patient record, but you use new Patient(). Rename the function to __construct to make it the class constructor. Now you can use new Patient(...).
Also, I think extending Patient in Clinic doesn't really make sense here, because you don't want to use the classes provided by Patient and extend them.
So remove extends Patient and your code should work now:
<?php
class Patient{
private $name;
private $age;
private $gender;
public function __construct($name, $age, $gender){
$this->name = $name;
$this->age = $age;
$this->gender = $gender;
}
public function getName(){
return $this->name;
}
public function getAge(){
return $this->age;
}
public function getGender(){
return $this->gender;
}
}
class Clinic {
private $patients = [];
public function getPatients(){
return $this->patients;
}
public function assignPatient($name, $age, $gender){
$this->patients[] = new Patient($name, $age, $gender);
}
public function deletePatient($index){
unset($this->patients[$index]);
}
}
$clinic = new Clinic();
$clinic->assignPatient("Patrick star",18,"Male");
$clinic->assignPatient("SpongeBob Squarepants",17,"Male");
$clinic->assignPatient("Eugene Krab",28,"Male");
$clinic->deletePatient(1);
print_r($clinic->getPatients());
Output:
Array
(
[0] => Patient Object
(
[name:Patient:private] => Patrick star
[age:Patient:private] => 18
[gender:Patient:private] => Male
)
[2] => Patient Object
(
[name:Patient:private] => Eugene Krab
[age:Patient:private] => 28
[gender:Patient:private] => Male
)
)
Tested on PHP 7.4 and PHP 8.0