Make a substitution between the values of two variables in PHP
<p>I was wondering if it could be possible to make a <strong>substitution</strong> between the values of two variables, in PHP.</p>

<p>I can explain it better:</p>

<pre><code>&lt;?php
    $a = "Cat";
    $b = "Dog";

    // The strange/non-existent function I am talking about //
    MakeSubstitution($a, $b);

    // After this (non-existent) function the values of the variables should be:
        // $a = "Dog"
        // $b = "Cat"
?&gt;
</code></pre>

<p>So, does it exist? I made searches but I found no results.
Thanks in advance.</p>
