__destruct() executed without unset

Question

Destruct function is automatically executed without unset the variable.

<?php

class cars
{
  public static $count=0;

  public function __construct($type, $year)
  {
     $this->type= $type;
     $this->year= $year;
     cars::$count++;
     return true;
   }

   public function __destruct()
   {
     echo "The " . $this->type . " is being deleted" . "<br>";
     cars::$count--;
   }
 }

$car1= new cars("Toyota Camry", 2014);
$car2= new cars("Nissan Altima", 2012);
$car3= new cars("Honda Accord", 2010);
$car4= new cars("Tesla Model X", 2015);
$car5= new cars("Tesla Model 3", 2016);

echo "The number of objects in the class is " . cars::$count;
echo "<br>";
unset($car4);
echo "The number of objects in the class is " . cars::$count;
?>

result of running this php file in browser is :

The number of objects in the class is 5    
The Tesla Model X is being deleted    
The number of objects in the class is 4
The Tesla Model 3 is being deleted    
The Honda Accord is being deleted    
The Nissan Altima is being deleted    
The Toyota Camry is being deleted

My question is, why is the __destruct function being executed on all objects without explicitly calling unset in the object?

Answer 1

The destructors are called because the PHP script is terminating. See the documentation of destructors:

The destructor method will be called [...], or in any order during the shutdown sequence.