How to exchange values of two variables without using a third one in php

Question

My question is very objective.
I need to exchange values of two variables without using a third one in php.
NOTE: Using array/array is not an option.

Researching I found a solution in linguagem c here, but I couldn’t get through to php. I also found that solution, however there is a bug quirky good.

This is my code:

        $change_provider = "Desenvolvimento Web";
        $change_receiver = "SEO(Search Engine Optimization)";

        $change_provider ^= $change_receiver ^= $change_provider ^= $change_receiver;

        print_r($change_provider); //string(19) "SEO(Search Engine O" 
        print_r($change_receiver); //string(19) "Desenvolvimento Web"

Notice that my output is missing some characters at the end. How to solve this problem ? I appreciate anyone who can help.

Answer 1

Basically this:

list( $a, $b ) = array( $b, $a );

In the newer versions:

list( $a, $b ) = [ $b, $a ];

It is important to note that both the above solutions and the use of a third variable are effective in the sense that they do not depend on memory relocation, as there is only an exchange of references, not values.

Skip the question a bit, but just for the record, note that PHP references are at a higher level than C pointers, which are memory positions. Regardless, the exchange of position is inexpensive in both languages.

Your solution, XOR Swap is for numbers only:

$change_provider ^= $change_receiver ^= $change_provider ^= $change_receiver;

It is based on a mathematical property of the XOR:

How the Xor Swap algorithm works?

_{As you have already noticed in your test, it works with strings, but only because they are treated as a sequence of bytes, see mention in the @Omine reply}

Answer 2

Given the conditions, the most appropriate form would be using XOR Swap algorithm. That is, the same that you presented in the question using bit-by-bit operators.

However, to function as desired, within the context of the question, it needs that both variables have the same amount of bytes. That is, you can use strings and not just numerical values. What matters is the amount of bytes.

_{note: The test presented in the question does not return a bug. The variable with a larger string is cut because it is larger than the other variable.}