<img id="myImg" src="someSrc.jpg" style="visibility:hidden" />
<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){ // eqv to page_load
   $("#myImg").fadeOut(0);
});

function validateValues(){
   $.ajax({

      url: "yourpage.php?yourparams=values",
      type: "get",
      success: function(result){

         if(result.toString() == "OK"){ // == "YOUR_PHP_RETURNED_VALUE"
            $("#myImg").css('visibility', 'visible');
            $("#myImg").fadeIn("slow");
         }else{
            // do other thing (maybe alert to user to check values)
         }

      } // success

   }); //$.ajax

} // validateValues


</script>