Aliasing a variable in PHP - php

Question

I have a library class class someClass{....}. I created an object for this class.
$objectA = someClass;
I would like to use an alias for $objectA to some thing like $objectB, hence my class is more meaningful.
PS: $objectB should point $objectA

Answer 1

$objectB = $objectA;
From the manual:
One of the key-points of PHP 5 OOP that is often mentioned is that
"objects are passed by references by default". This is not completely
true. This section rectifies that general thought using some examples.
A PHP reference is an alias, which allows two different variables to
write to the same value. As of PHP 5, an object variable doesn't
contain the object itself as value anymore. It only contains an object
identifier which allows object accessors to find the actual object.
When an object is sent by argument, returned or assigned to another
variable, the different variables are not aliases: they hold a copy of
the identifier, which points to the same object.
<?php
class A {
public $foo = 1;
}
$a = new A;
$b = $a; // $a and $b are copies of the same identifier
// ($a) = ($b) = <id>
$b->foo = 2;
echo $a->foo."\n";
$c = new A;
$d = &$c; // $c and $d are references
// ($c,$d) = <id>
$d->foo = 2;
echo $c->foo."\n";
$e = new A;
function foo($obj) {
// ($obj) = ($e) = <id>
$obj->foo = 2;
}
foo($e);
echo $e->foo."\n";
?>
The above example will output:
2
2
2

Answer 2

I like John Conde's answer. I would like to add the following (to make it more straightforward):
In PHP almost anything can be "referenced". It is a similar concept to a "pointer" for old folks like me who came from the roots of technology programming in C and ASM.
A "pointer" is the address of the physical location of something in memory. By knowing it, you can reference that content without using the variable in the context.
In PHP, if you precede objects, structures, or variables with the symbol "&" you are telling the interpreter that you want the reference of the content and not the content itself. When associating it to another object, structure, or variable, instead of making a copy of it in another memory allocation point, the PHP interpreter will reference it to the same memory location as the original. Mainly, you will end up with two items pointing to the same location in RAM.
You can reference variables, structures, and objects in PHP like this:
$variable = "Variable Content";
$alias = &$variable;
echo $alias;
The above code should print Variable Content.
Please, notice that $alias = &$variable; is NOT the same as $alias = $variable; (without the "&"). In the first case, PHP will duplicate the content of $variable in $alias, and you will have two identical values in different locations of RAM being pointed by different variables. The second case, using "&", is a single content with two pointers that are independent but reference to the same location in RAM.
Similarly with how it happens with two specific variables, if you unset either of them ($variable or $alias) it won't unset the reference, which means the other will continue working. But, if you modify any, it will modify the content for both variables because they are looking to the same physical location in RAM to retrieve the content when used.
Think about this as analogous to the Unix unlink call. The same rule applies to objects and structures. Everything is referenceable.
And, YES, you can have multiple references to the same single content.
If you are now suddenly thinking about a "garbage collection" (GC) nightmare, well, so you got it. :)
More at https://www.php.net/manual/en/language.references.php
Those are similar in concept, varying only in terms of implementation and language model:
Referecences = Alias = Pointer