e function tests
whether each of the array indices is set. If an index does not exist it
is set to NULL, or whatever you’ve specified as the default value via
the third parameter.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$array</span> <span class="o">=</span> <span class="k">array</span><span class="p">(</span>
        <span class="s1">&#39;color&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;red&#39;</span><span class="p">,</s