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Types of Constructor in PHP 

A constructor in PHP is a special method that runs automatically when an object is created. It helps set initial values and prepare the object for use. PHP mainly has three types of constructors:

  1. Default Constructor
  2. Parameterized Constructor
  3. Copy Constructor

Default Constructor

A default constructor is a constructor without any parameters. It runs automatically when you create an object and is used to set default values or display a message.

Example:

<?php
class Student
{
    // Default constructor
    public function __construct()
   {
        echo "A new student is created!<br>";
    }
}

// Creating an object
$student1 = new Student(); // Constructor runs automatically
?>

Explanation:

  • The constructor runs when $student1 is created.
  • No parameters are passed; it just prints a message.

Parameterized Constructor

A parameterized constructor accepts parameters to initialize object properties. It’s useful when you want to pass values during object creation.

Example:

<?php
class Student 
{
    public $name;
    public $age;

    // Parameterized constructor
    public function __construct($name, $age)
   {
        $this->name = $name;  // Set name
        $this->age = $age;    // Set age
        echo "Student $name is $age years old. <br>";
    }
}

// Creating objects with parameters
$student1 = new Student("Raj", 20);
$student2 = new Student("Simran", 22);
?>

 Explanation:

  • $name and $age are passed as arguments.
  • The constructor sets the object’s properties.

Copy Constructor (Simulated in PHP)

PHP does not have a built-in copy constructor, but you can simulate it by creating a constructor that copies properties from another object.

<?php
class Student 
{
    public $name;

    // Parameterized constructor
    public function __construct($name) 
    {
        $this->name = $name;
    }

    // Copy constructor (simulated)
    public static function copy(Student $student)
   {
        return new Student($student->name);
    }
}

// Create original object
$student1 = new Student("Raj");

// Create copy using the copy constructor
$student2 = Student::copy($student1);

echo "Original: $student1->name<br>"; // Raj  
echo "Copy: $student2->name<br>";     // Raj  
?>

 Explanation:

  • copy() takes another Student object and creates a new one with the same data.
  • Both objects have the same name but are independent.

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