Constructors

Constructors

Constructors, Destructors and Property Promotion

__construct() runs right after new allocates the object. With constructor property promotion (PHP 8.0), a parameter carrying a visibility keyword declares and assigns the property in one step. __destruct() runs the moment the last reference goes, or at shutdown for objects still alive.

Promoted parameters, and exactly when a destructor runsPHP

<?php
class Order {
  public function __construct(
    public readonly int $id,            // promoted: declared and assigned for you
    private string $status = 'pending', // promoted with a default
    string $note = '',                  // no visibility: an ordinary argument
  ) { echo "open #$id $note\n"; }
  public function __destruct() { echo "close #{$this->id} ({$this->status})\n"; }
}
$a = new Order(5001, note: 'gift wrap');
$b = $a;
unset($a);                              // $b still holds the object
echo "after unset\n";
$b = null;                              // last reference gone: destructor runs now
echo "end of script\n";

Output

open #5001 gift wrap
after unset
close #5001 (pending)
end of script

Use destructors to release what the object holds, never for work that must happen, such as a commit. readonly is covered in Subsection 4.11.5.

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