Add additional data to array
<p>I have associative array which looks like this.</p>

<pre><code>$arr = array(
   "FIRST" =&gt; 1,
   "SECOND =&gt; 2,
   "FOURTH =&gt; 4
);
</code></pre>

<p>The idea is how to "add" data to this array depending of expression.
Here is what I'm trying to do:</p>

<pre><code>if(3 == 3) {
  $str = array("THIRD" =&gt; 3);
}

 $arr = array(
       "FIRST" =&gt; 1,
       "SECOND =&gt; 2,
       $str,
       "FOURTH =&gt; 4
    );
</code></pre>

<p>The problem is that the code above add $str as an array in $arr, not like "THIRD" => 3</p>
