clone versus no clone

Have a read of this article:
https://www.experts-exchange.com/Web_Development/Web_Languages-Standards/PHP/A_12310-PHP-Variables-and-References.html

The real-world example might exist in an environment where an object gets mutated and you need a second copy of the object.  Perhaps you call a method after property  #1 is added to the object, then another method after property #2, etc.  If you want a record of the state of the object after each property is added you can clone the object after each addition.

You can also nullify the clone() method, as in a Singleton design pattern.

<?php // RAY_database_singleton.php
error_reporting(E_ALL);


// SINGLETON DATA BASE CONNECTION CLASS
class Database
{
    // CLASS PROPERTIES ARE ALL PRIVATE
    private static $connection;
    private static $instance;

    // CONNECTION VALUES
    const DB_HOST = 'localhost';
    const DB_USER = '?';
    const DB_PASS = '?';
    const DB_NAME = '?';

    // NULLIFY THE CLONE
    final private function __clone() {}

    // OUR ONLY PUBLIC METHOD RETURNS THE CONNECTION
    public static function getConnection()
    {
        if (!self::$instance) self::$instance = new self();
        return self::$connection;
    }

    // CONSTRUCTOR CREATES THE CONNECTION
    private function __construct()
    {
        self::$connection
        = new mysqli
        ( self::DB_HOST
        , self::DB_USER
        , self::DB_PASS
        , self::DB_NAME
        )
        ;
        if (self::$connection->connect_error)
        {
            trigger_error(self::$connection->connect_error, E_USER_ERROR);
        }
    }
}

$mysql1 = database::getConnection();
$mysql2 = database::getConnection();


// PROVE THAT THESE ARE THE SAME OBJECT http://php.net/manual/en/language.oop5.object-comparison.php
if ($mysql1 === $mysql2) echo 'EQUAL';

// SHOW THE OBJECT
var_dump($mysql1);

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Running in a debugger
name--------------- value------------------ type
$mysql1-----------none(empty)----------object(myqli)

and this was output
EQUALobject(mysqli)#2 (0) { }

If you want a record of the state of the object after each property is added you can clone the object after each addition.

Okay I understand clone alittle better when you have example (if coder needs a snapshot) so maybe real world is windows os system restore

Or maybe a boss/client told you to make a snapshot, if so why?

Why did a boss tell you to make a snapshot?   I dunno.  Ask the boss!

:-)

~Ray

I meant to ask. Why would you use clone? In what type of project is clone used?

Does arr[] hold 3 objects. Would $arr[1] be ray

Arrays are numbered starting at zero.  Numeric array keys are frequently subject to being reset.  The array keys are shown in the print_r() output.  Just install the script and run it to see what it does with the data.  Easy!

$object->id    = "1";
$object->fname = "Ray";
$object->lname = "Paseur";
$object->work  = "Programmer";
$object->func  = "testData";
$arr[] = /*clone*/ $object;

$object->id    = "2";
$object->fname = "John";
$object->lname = "James";
$object->work  = "Student";
$arr[] = /*clone*/ $object;

$object->id    = "3";
$object->fname = "Dave";
$object->lname = "Baldwin";
$object->work  = "Expert";
$arr[] = /*clone*/ $object;

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only had the last object repeated 3 times
so now I understand clone better

thanks.

Thanks for the points!