How to check if variable is empty in phing build xml?
<p>I referred <a href="https://www.phing.info/docs/guide/trunk/PhpEvalTask.html" rel="nofollow">the documentation</a> and tried this - </p>

<pre><code>&lt;php function="empty" returnProperty="productionSameAsExpectedBranch"&gt;
    &lt;param value="${productionDeviationFromExpectedBranch}"/&gt;
&lt;/php&gt;
</code></pre>

<p>But it gives error - </p>

<blockquote>
  <p>[php] Calling PHP function: empty()
  [PHP Error] call_user_func_array() expects parameter 1 to be a valid callback, function 'empty' not found or invalid function name [line 125 of /usr/share/pear/phing/tasks/system/PhpEvalTask.php]</p>
</blockquote>