PHP Destructor: __destruct() and Object Cleanup

A destructor is the opposite of a constructor. PHP calls __destruct() when an object is about to be removed from memory.

index.php

PHP

<?php
class Connection
{
    public function __construct(private string $name)
    {
        echo "Opening {$this->name}\n";
    }

    public function __destruct()
    {
        echo "Closing {$this->name}\n";
    }
}

$a = new Connection("A");
echo "Doing work\n";
unset($a);          // the object is destroyed here
echo "After unset\n";

Output

OUTPUT

Opening A
Doing work
Closing A
After unset

When is it called?

When the last reference to the object disappears (unset(), assigning null, or a variable going out of scope).
When the script ends, for objects that still exist.

index.php

PHP

<?php
class Note
{
    public function __construct(private string $text) {}

    public function __destruct()
    {
        echo "Bye, {$this->text}\n";
    }
}

function make(): void
{
    $n = new Note("local");
    echo "Inside function\n";
}   // $n is destroyed here

make();
echo "End of script\n";
$later = new Note("global");

Output

OUTPUT

Inside function
Bye, local
End of script
Bye, global

What to use it for

Closing a file or connection that the object opened.
Releasing a lock.

What not to do

Do not rely on it for important work. If the script crashes or is killed, the destructor may not run. Save data explicitly, not in a destructor.
Do not throw exceptions from it.
Do not put slow code in it. It runs at the end of the request.

Explicit close methods are better

For resources, give the class a close() method and call it yourself, ideally inside finally.

index.php

PHP

<?php
class Logger
{
    private $handle;

    public function __construct(string $file)
    {
        $this->handle = fopen($file, "a");
    }

    public function write(string $message): void
    {
        fwrite($this->handle, $message . PHP_EOL);
    }

    public function close(): void
    {
        fclose($this->handle);
    }
}

$logger = new Logger("run.log");

try {
    $logger->write("Started");
} finally {
    $logger->close();
}

echo "Done";

Output

OUTPUT

Done

PHP cleans up for you

PHP closes files and frees memory at the end of each request. Destructors are rarely needed in web code, so you will see few of them in real projects.

info

Short-lived by design

A PHP web request starts, runs and ends in a fraction of a second. That is why PHP developers care less about destructors than developers of long-running programs do.