Swapping of two numbers in PHP

<?php
class SwapExample {

    public function swap() {
        $a = 3;
        $b = 6;

        echo("The value of a before swap is " . $a . "\n");
        echo("The value of b before swap is " . $b . "\n");

        // Swapping of two numbers using temp variable
        $temp = $a;
        $a = $b;
        $b = $temp;

        echo("The value of a after swap is " . $a . "\n");
        echo("The value of b after swap is " . $b . "\n");
    }
}

$obj = new SwapExample();
$obj->swap();

<?php
class SwapExample {

    public function swap() {
        $a = 3;
        $b = 6;

        echo("The value of a before swap is " . $a . "\n");
        echo("The value of b before swap is " . $b . "\n");

    	// Swapping of two numbers using arithmetic operations
        $a = $a + $b;
        $b = $a - $b;
        $a = $a - $b;

        echo("The value of a after swap is " . $a . "\n");
        echo("The value of b after swap is " . $b . "\n");
    }
}

$obj = new SwapExample();
$obj->swap();

<?php
class SwapExample {

    public function swap() {
        $a = 3;
	    $b = 6;

        echo("The value of a before swap is " . $a . "\n");
        echo("The value of b before swap is " . $b . "\n");

        // Swapping of two numbers using arithmetic operations
        $b = $a + $b - ($a = $b);

        echo("The value of a after swap is " . $a . "\n");
        echo("The value of b after swap is " . $b . "\n");
    }
}

$obj = new SwapExample();
$obj->swap();

<?php
class SwapExample {

    public function swap() {
        $a = 3;
        $b = 6;

        echo("The value of a before swap is " . $a . "\n");
        echo("The value of b before swap is " . $b . "\n");

        // Swapping of two numbers 
        // using exclusive OR operation (i.e. XOR)
        $a = $a ^ $b;
        $b = $a ^ $b;
        $a = $a ^ $b;

        echo("The value of a after swap is " . $a . "\n");
        echo("The value of b after swap is " . $b . "\n");
    }
}

$obj = new SwapExample();
$obj->swap();