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PHP find output programs (Constructors and Destructors) | set 2

Find the output of PHP programs | Constructors & Destructors | Set 2: Enhance the knowledge of PHP Constructors & Destructors by solving and finding the output of some PHP programs.
Submitted by Nidhi, on January 28, 2021

Question 1:

<?php
    class Sample
    {
        private $A;
        private $B;
    
        public function Sample()
        {
            $this->A = 10;
            $this->B = 20;
        }
        public function Sample($A, $B)
        {
            $this->A = $A;
            $this->B = $B;
        }
        public function print ()
        {
            echo "A: $this->A<br>";
            echo "B: $this->B<br>";
        }
    }
    
    $OB1 = new Sample();
    $OB1->print();
    
    $OB2 = new Sample(30, 40);
    $OB2->print();
?>

Output:

PHP Fatal error:  Cannot redeclare Sample::Sample() 
in /home/main.php on line 12

Explanation:

The above program will generate a fatal error because we cannot perform constructor overloading using PHP.

Question 2:

<?php
class Sample
{
    private $A;
    private $B;

    public function Sample():
        int
        {
            $this->A = 10;
            $this->B = 20;
            return 0;
        }
        public function print ()
        {
            echo "A: $this->A<br>";
            echo "B: $this->B<br>";
        }
    }

    $OB1 = new Sample();
    $OB1->print();
?>

Output:

PHP Fatal error:  Constructor Sample::Sample() cannot 
declare a return type in /home/main.php on line 2

Explanation:

The above program will generate syntax error because the constructor does not support return type in PHP.

Question 3:

<?php
    class Sample
    {
        public function Sample()
        {
            print ("Constructor Called<br>");
        }
        public function ~Sample()
        {
            print ("Destructor Called<br>");
        }
    }
    
    $OB = new Sample();
?>

Output:

PHP Parse error:  syntax error, unexpected '~' 
in /home/main.php on line 8

Explanation:

The above program will generate syntax error, we cannot call destructor using tilde '~' symbol. To implement destructor in a class, we need to use the __destruct() magic function.

Question 4:

<?php
    class Sample
    {
        public function Sample()
        {
            print ("Constructor Called<br>");
        }
        public function __DESTRUCT()
        {
            print ("Destructor Called<br>");
        }
    }
    
    $OB = new Sample();
?>

Output:

Constructor Called
Destructor Called

Explanation:

In the above program, we created a class Sample that contains constructor and destructor, And we created an object of Sample class then constructor and destructor both will be called and print messages on the webpage.

A constructor is called when an object gets created while the destructor is called when the scope of the object gets finished.

Question 5:

<?php
    class Sample
    {
        public $VAL;
    
        public function __construct()
        {
            $this->VAL = 10;
        }
        public function Sample($V)
        {
            $this->VAL = $V;
        }
        public function print ()
        {
            print ("$this->VAL<br>");
        }
    }
    
    $OB1 = new Sample();
    $OB2 = new Sample(20);
    
    $OB1->print();
    $OB2->print();
?>

Output:

10
10

Explanation:

In the above program, we defined two constructors, default constructor using __construct() magic function and another is parameterized constructor. Then we created two objects $OB1 and $OB2, both will call default constructor __construct. If we defined more than one constructor in a class, but constructor defined using __construct() will always call, other constructors can be defined but cannot be called.



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