 <p>If there is some PHP behind, the problem could be calling a function empty($var) in this way:</p> <pre><code>if(empty($var = getMyVar())) { ... } </code></pre> <p>Instead of this You should call it this way:</p> <pre><code>$var = getMyVar(); if(empty($var)) { ... } </code></pre> <p>Or better (as <strong>deceze</strong> has pointed out)</p> <pre><code>if(!getMyVar()) { ... } </code></pre> <p>Problem causes also other similar functions (isset, is_a, is_null, etc).</p>