Error occurs with while Loop PHP / MySQL NuSOAP - web-services

Question

I have created a PHP / MySQL based web service. I wrote client.php as mentioned here
and server.php as below:
<?php
require_once("lib/nusoap.php");
$host = $_SERVER['HTTP_HOST'];
$miURL = 'http://'.$host.'/WS-Demo';
$server = new nusoap_server();
$server->configureWSDL('L3M_WebService', $miURL);
$server->wsdl->schemaTargetNamespace=$miURL;
$server->register('getDemoData',
array('fldpara' => 'xsd:Array', 'tblpara' => 'xsd:Array', 'cndpara' => 'xsd:Array'),
array('return' => 'xsd:string'),
$miURL);
function decryptRJ256($string_to_decrypt)
{
$key = 'salt_key - I';
$iv = 'salt_key - II';
$string_to_decrypt = base64_decode($string_to_decrypt);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $string_to_decrypt, MCRYPT_MODE_CBC, $iv);
$rtn = rtrim($rtn, "\4");
return($rtn);
}
function encryptRJ256($string_to_encrypt)
{
$key = 'salt_key - I';
$iv = 'salt_key - II';
$rtn = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $string_to_encrypt, MCRYPT_MODE_CBC, $iv);
$rtn = base64_encode($rtn);
return($rtn);
}
function getDemoData($flds, $tbls, $cnds){
$mysqli = new mysqli("localhost", "root", "", "test");
for($i=0;$i< count($flds); $i++) {
$flds[$i] = decryptRJ256($flds[$i]);
}
for($i=0;$i< count($tbls); $i++) {
$tbls[$i] = decryptRJ256($tbls[$i]);
}
for($i=0;$i< count($cnds); $i++) {
$cnds[$i] = decryptRJ256($cnds[$i]);
}
if(! empty($flds)) {
$what = implode(", ", $flds);
} else {
$what = "*";
}
if(! empty($tbls)) {
$from = implode(", ", $tbls);
}else {
$err = 1;
}
if(! empty($cnds)) {
$cond = " WHERE ";
$cond .= $cnds[0] . " = '" . $cnds[1] . "'";
} else {
$cond = "";
}
$sql = "SELECT ".$what." FROM ".$from . $cond;
$rsGetData = $mysqli->query($sql);
$responseData = '<?xml version="1.0" encoding="UTF-8"?>
<L3MDataSets>';
while($rowGetData = $rsGetData->fetch_assoc()) {
$responseData .= '<L3DataSet>';
foreach($rowGetData as $k => $v) {
$responseData .= '<' . $k . '>' . $v . '</' . $k . '>';
}
$responseData .= '</L3DataSet>';
}
$responseData .= '</L3MDataSets>';
$responseData = encryptRJ256($responseData);
$responseString = new soapval('return', 'xsd:string', $responseData );
return $responseData;
}
$HTTP_RAW_POST_DATA = isset($HTTP_RAW_POST_DATA) ? $HTTP_RAW_POST_DATA : '';
$server->service($HTTP_RAW_POST_DATA);
?>
From the Above code in the getDemoData function, if I remove the while loop, it gives the proper output. But when I put back the while loop it shows me output as "-Error: Response not of type text/xml: text/html" even if the SQL query is correct. I have copied and paste the generated SQL query which works in phpMyAdmin.