checking on strings values</p>
<div class="variablelist"><table border="0"><col align="left" /><tbody><tr><td><span class="term"><i><tt>ctxt</tt></i>:</span></td><td>the expressions context</td></tr><tr><td><span class="term"><i><tt>expr</tt></i>:</span></td><td>the 0 terminated string</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>a new expression or NULL in case of failure</td></tr></tbody></table></div><h3><a name="xmlExpRef" id="xmlExpRef"></a>Function: xmlExpRef</h3><pre cl