add key to associative array if key is not found
<p>Given a PHP associative array like this one:</p>

<pre><code>$a = array(
    'color' =&gt; 'red',
    'taste' =&gt; 'sweet',
    'shape' =&gt; 'round',
    'name'  =&gt; 'apple'
);
</code></pre>

<p>I want to search a key and, if not found, I want to add 'myKey'=>0. Which is the best way to do such a thing?</p>
