PHP Destructor

In PHP, a destructor is a special method that is automatically called when an object is destroyed or goes out of scope. Destructors are useful for cleaning up resources such as closing files, releasing memory, or closing database connections.

Syntax

The destructor method is defined using the __destruct keyword. Here is the basic syntax of a destructor in PHP:

class MyClass {
    // Constructor
    public function __construct() {
        echo "Constructor called\n";
    }

    // Destructor
    public function __destruct() {
        echo "Destructor called\n";
    }
}

// Creating an instance of MyClass
$obj = new MyClass();

Example 1: Basic Destructor

In this example, the destructor will be called when the script ends or when the object is explicitly unset.

class MyClass {
    // Constructor
    public function __construct() {
        echo "Constructor called\n";
    }

    // Destructor
    public function __destruct() {
        echo "Destructor called\n";
    }
}

// Creating an instance of MyClass
$obj = new MyClass();

// Unsetting the object to trigger the destructor
unset($obj);

echo "Script end\n";

Output:

Constructor called
Destructor called
Script end

Example 2: Destructor with Resource Cleanup

Destructors can be used to clean up resources such as closing a file handle.

class FileHandler {
    private $file;

    // Constructor
    public function __construct($filename) {
        $this->file = fopen($filename, 'w');
        echo "File opened\n";
    }

    // Destructor
    public function __destruct() {
        fclose($this->file);
        echo "File closed\n";
    }

    public function write($data) {
        fwrite($this->file, $data);
    }
}

// Creating an instance of FileHandler
$fileHandler = new FileHandler('example.txt');
$fileHandler->write("Hello, World!\n");

echo "Script end\n";

Output:

File opened
Script end
File closed

In this example, the file is opened when the FileHandler object is created, and it is closed automatically when the object is destroyed at the end of the script.

Example 3: Destructor in Inheritance

Destructors in parent and child classes can both be called when an object is destroyed.

class ParentClass {
    public function __destruct() {
        echo "Parent destructor called\n";
    }
}

class ChildClass extends ParentClass {
    public function __destruct() {
        echo "Child destructor called\n";
        parent::__destruct(); // Call parent destructor explicitly if needed
    }
}

// Creating an instance of ChildClass
$obj = new ChildClass();

echo "Script end\n";

Output:

Script end
Child destructor called
Parent destructor called

In this example, the destructor of the child class is called first, followed by the destructor of the parent class.

Destructors are a powerful feature in PHP that allows for efficient resource management and cleanup. They ensure that resources are properly released when objects are no longer needed.