php call standard function by string
<p>I need to call a PHP standard function from a string</p>

<p>Example:</p>

<pre><code>$param = "parameter";
$functionname = "createimagefromjpg";
//call the function (with a parameter)
</code></pre>

<p>Anyone has an idea how I can do this?
It can't be done with <code>call_user_func()</code> because it is a standard function.</p>
