Is it a bug in PHP with assignment by reference? [duplicate] - php

Question

This question already has answers here:
PHP param by ref => assign to ref = NULL
(1 answer)
PHP's assignment by reference is not working as expected
(7 answers)
Closed 8 years ago.
Here is the simplified version of code that might be revealing a PHP bug
class AClass
{
public static $prop = "Hi";
}
function assignRef (&$ref)
{
$ref = &AClass::$prop;
echo "inside assignRef: $ref\n";
}
$ref = "Hello";
assignRef($ref);
echo "outside: $ref\n";
This prints out
inside assignRef: Hi
outside: Hello
Shouldn't $ref had been assigned by reference to $prop static variable of the AClass class and become "Hi" not just inside assignRef function but also outside of it?

Answer 1

The class in your example is irrelevant, simplified version that produces the same output:
function assignRef (&$ref)
{
$prop = 'Hi';
$ref = &$prop;
echo "inside assignRef: $ref\n";
}
$ref = "Hello";
assignRef($ref);
echo "outside: $ref\n";
What is happening is that when assigning by reference inside the function ($ref = &$prop;) you are just changing what one variable is pointing to, not changing the value of what it was originally pointing to nor changing any other references to that original value.
You effectively have two variables called $ref in this example - one inside the function, and one outside the function. You are changing what the variable inside the function points to, leaving the other variable pointing to the original (unchanged) value.
Consider the following code:
$a = 'a';
$b = 'b';
$c = 'c';
$a = &$b;
$b = &$c;
echo "$a / $b / $c";
This results in output of b / c / c, rather than what you might expect c / c / c. This happens for the same reason - assignment by reference does not affect the value originally referenced nor change any other references, meaning any other variables pointing to the original value are unchanged.
If you want to change the value, rather than creating a new reference to another value, you must use normal assignment (=). Alternatively, you could change all references.