Is there a PHP function for swapping the values of two variables?

Question

Say for instance I have ...

$var1 = "ABC"
$var2 = 123

and under certain conditions I want to swap the two around like so...

$var1 = 123
$var2 = "ABC"

Is there a PHP function for doing this rather than having to create a 3rd variable to hold one of the values then redefining each, like so...

$var3 = $var1
$var1 = $var2
$var2 = $var3

For such a simple task its probably quicker using a 3rd variable anyway and I could always create my own function if I really wanted to. Just wondered if something like that exists?

Update: Using a 3rd variable or wrapping it in a function is the best solution. It's clean and simple. I asked the question more out of curiosity and the answer chosen was kind of 'the next best alternative'. Just use a 3rd variable.

Answer 1

TL;DR

There isn't a built-in function. Use swap3() as mentioned below.

Summary

As many mentioned, there are multiple ways to do this, most noticable are these 4 methods:

function swap1(&$x, &$y) {
    // Warning: works correctly with numbers ONLY!
    $x ^= $y ^= $x ^= $y;
}
function swap2(&$x, &$y) {
    list($x,$y) = array($y, $x);
}
function swap3(&$x, &$y) {
    $tmp=$x;
    $x=$y;
    $y=$tmp;
}
function swap4(&$x, &$y) {
    extract(array('x' => $y, 'y' => $x));
}

I tested the 4 methods under a for-loop of 1000 iterations, to find the fastest of them:

• swap1() = scored approximate average of 0.19 seconds.
• swap2() = scored approximate average of 0.42 seconds.
• swap3() = scored approximate average of 0.16 seconds. Winner!
• swap4() = scored approximate average of 0.73 seconds.

And for readability, I find swap3() is better than the other functions.

Note

• swap2() and swap4() are always slower than the other ones because of the function call.
• swap1() and swap3() both performance speed are very similar, but most of the time swap3() is slightly faster.
• Warning: swap1() works only with numbers!