ring</em>) &#8211; Function name</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">TRUE if the function can be used, FALSE if not</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">bool</p>
</td>
</tr>
</tbody>
</table>
<p>Returns TRUE if a function exists and is usable, FALSE otherwise.</p>
<p>This function runs a <code class="docutils literal"><span cl