PHP Destructor

Cleaning up when objects are destroyed

🧹 What is a Destructor?

A destructor is a special method that automatically runs when an object is destroyed or the script ends. It's used for cleanup tasks like closing files, database connections, or freeing resources. 


<?php
class FileHandler {
    public $filename;
    
    public function __construct($filename) {
        $this->filename = $filename;
        echo "File opened: $filename
";
    }
    
    public function __destruct() {
        echo "File closed: $this->filename
";
    }
}

$file = new FileHandler("data.txt");
// Destructor runs automatically at script end
?>

Output:

File opened: data.txt

File closed: data.txt

Destructor Features

🔄

Auto-Execute

Runs when object is destroyed or script ends 

public function __destruct() {
    // Cleanup code
}
🧹

Cleanup Tasks

Close connections and free resources 

public function __destruct() {
    $this->close();
}
📝

No Parameters

Destructors cannot accept parameters 

// Correct
public function __destruct() {
}
⏱️

Timing

Called when no references to object exist 

unset($obj);
// Destructor runs

🔹 Basic Destructor

The destructor method is named __destruct() with two underscores. It's automatically called when the object is no longer needed or when the script finishes execution. 

<?php
class Message {
    public $text;
    
    public function __construct($text) {
        $this->text = $text;
        echo "Object created: $text
";
    }
    
    public function __destruct() {
        echo "Object destroyed: $this->text
";
    }
}

$msg1 = new Message("Hello");
$msg2 = new Message("World");
echo "Script running...
";
// Destructors run automatically at end
?>

Output:

Object created: Hello

Object created: World

Script running...

Object destroyed: World

Object destroyed: Hello

🔹 Manual Object Destruction

You can manually destroy an object using unset() . This immediately triggers the destructor instead of waiting for the script to end. 

<?php
class Connection {
    public $name;
    
    public function __construct($name) {
        $this->name = $name;
        echo "Connection opened: $name
";
    }
    
    public function __destruct() {
        echo "Connection closed: $this->name
";
    }
}

$conn = new Connection("Database");
echo "Working with connection...
";
unset($conn); // Manually destroy object
echo "After unset
";
?>

Output:

Connection opened: Database

Working with connection...

Connection closed: Database

After unset

🔹 Destructor for Resource Management

Destructors are commonly used to ensure resources like file handles or database connections are properly closed, preventing memory leaks and resource exhaustion. 

<?php
class Logger {
    private $logFile;
    private $filename;
    
    public function __construct($filename) {
        $this->filename = $filename;
        $this->logFile = fopen($filename, 'a');
        echo "Log file opened: $filename
";
    }
    
    public function write($message) {
        if ($this->logFile) {
            fwrite($this->logFile, date('Y-m-d H:i:s') . " - $message\n");
            echo "Logged: $message
";
        }
    }
    
    public function __destruct() {
        if ($this->logFile) {
            fclose($this->logFile);
            echo "Log file closed: $this->filename
";
        }
    }
}

$logger = new Logger("app.log");
$logger->write("Application started");
$logger->write("User logged in");
// Destructor automatically closes file
?>

Output:

Log file opened: app.log

Logged: Application started

Logged: User logged in

Log file closed: app.log

🔹 Practical Example

This example demonstrates how constructors and destructors work together to manage the lifecycle of an object from creation to destruction. 

<?php
class Session {
    public $sessionId;
    public $username;
    
    public function __construct($username) {
        $this->sessionId = uniqid();
        $this->username = $username;
        echo "Session started for $username (ID: $this->sessionId)
";
    }
    
    public function activity($action) {
        echo "$this->username performed: $action
";
    }
    
    public function __destruct() {
        echo "Session ended for $this->username (ID: $this->sessionId)
";
    }
}

$session = new Session("Alice");
$session->activity("Viewed dashboard");
$session->activity("Updated profile");
echo "Logging out...
";
// Destructor runs automatically
?>

Output:

Session started for Alice (ID: 65c7f8a9b1234)

Alice performed: Viewed dashboard

Alice performed: Updated profile

Logging out...

Session ended for Alice (ID: 65c7f8a9b1234)

🧠 Test Your Knowledge

When is a destructor automatically called?