php - Call jquery alert only when an error occured during submit -

i have small script display error inside div when error occured in form.

//php

if(empty($date_from) && empty($date_to)) {     $error = "no search query";  } elseif(empty($date_from) && !empty($date_to)) {     $error = "specify end date search"; } elseif(!empty($date_from) && empty($date_to)) {     $error ="specify start date search"; } else {     $error ="som error"; } 

//form

<p>date: <input type="text" class="datepicker" name="from_date" id="field1"></p> <p>to</p> <p>date: <input type="text" class="datepicker" name="to_date" id="field2"></p><br /> 

//script

<script> window.settimeout(function() { $("#alert").fadeto(800, 0).slideup(900, function(){ $(this).remove();  }); }, 3000); </script> 

this automatically display error during refresh or every time page reloaded.what want show errors after user submits button, , when error occured.

wrap conditions in here

if( isset($_post['submitbuttonname']) ) {     // if else statements error here }