Can't invoke a closure wrapped in a closure?
<p>If I wrap a closure in another closure, I can't invoke the nested closure. Why not? I think an example illustrates the problem best.</p>

<p>This PHP code:</p>

<pre><code>function FInvoke($func) {
    $func();
}

FInvoke(function () { echo "Direct Invoke Worked\n"; });
</code></pre>

<p>Works as expected and prints "Direct Invoke Worked".</p>

<p>However, If I slightly modify it to add another level of indirection, it fails:</p>

<pre><code>function FInvoke($func) {
    $func();
}

function FIndirectInvoke($func) {
    FInvoke(function () {
        $func();
    });
}

FIndirectInvoke(function () { echo "Never makes it here"; });
</code></pre>

<p>The failure message is "Fatal error: Function name must be a string in file.php on line X"</p>
