Tienes que usar el fetch_array
Código PHP:
<?php
$response = array();
include 'Conexion.php';
$query = mssql_query("SELECT * FROM assi.dbo.CLIENT WHERE NOMEMPRESA = 'Roger Calibnet'");
if (mssql_num_rows($query) > 0){
$array_datos = mssql_fetch_array($query);
$response["client"] = utf8_encode($array_datos ["nomempresa"]);
$response["success"] = 1;
$response["query"] = $query;
echo json_encode($response);
echo '<pre>';
print_r($array_datos );
echo '</pre>';
}else{
$response["success"] = 0;
$response["cause"] = "NO_RESULTS";
$response["message"] = "LA QUERY NO DEVUELVE FILAS";
echo json_encode($response);
}
?>
PD: Que "query" sea null, es pq es un #Resource, no un valor ;)