Validation using Jquery/$.ajax and php
===

I have a form with radios and trying to validate starting with jq/$.ajax and then posting info in php.

form.php

    <tr>
      <td class="h"><span class="txt_wht">t1</span></td>
            <input type="hidden" name="gm[0]" value="t1" />
      <td class="vs"><span class="txt_yel_sm">vs</span></td>
      <td class="a"><span class="txt_wht">t2</span></td>
            <input type="hidden" name="gm[1]" value="t2" />
    
      <td><input type="radio" name="g1" value="a" /></td>
      <td><input type="radio" name="g1" value="b" /></td>
      <td><input type="radio" name="g1" value="c" /></td>
      </tr>
    <tr>
      <td class="h"><span class="txt_wht">t1</span></td>
            <input type="hidden" name="gm[0]" value="t1" />
      <td class="vs"><span class="txt_yel_sm">vs</span></td>
      <td class="a"><span class="txt_wht">t2</span></td>
            <input type="hidden" name="gm[1]" value="t2" />
    
      <td><input type="radio" name="g2" value="a" /></td>
      <td><input type="radio" name="g2" value="b" /></td>
      <td><input type="radio" name="g2" value="c" /></td>
     </tr>

validade.js

    //global vars

    form.submit(function(){
        if(validate1() && validate2()){
        //vars
        var exst_email = $('#exst_email').attr('value');
        var g1 = $("input[name='g1']:checked").attr('value');
        //more vars
        
      $.ajax({
      type: "post",
      url: "scripts/sbmt.php",
      data: "exst_email="+ exst_email,
      success: function (exst_rsp){
    
        //if its not exist
        if(exst_rsp == "not_exist"){
        valInfo.text("Error1!");
        valInfo.addClass("error");
        email_reg_err = true;
        }
        else{
        valInfo.text("");
        valInfo.removeClass("error");
        email_reg_err = false;
        }
    //more validation with error msgs
    
    //validate 1 & validate 2 functions
and sbmt.php

    session_start();
    // connect to db
    require_once('conn.php');

    if($stmt = $mysqli->prepare('SELECT email FROM table WHERE email=?')){
       $stmt->bind_param("s", $_POST['email']); 
       $stmt->execute();
       $stmt->store_result();

       $numRows = $stmt->num_rows();
       if($numRows < 1){
           echo 'not_exist';
           exit();
       }
       $stmt->close();
    }
    //more validation
Now,

1. Due to Dreamweaver, I know that I don't have typing errors or unclosed tags.

2. My validate 1 & 2 functions are working fine.

3. Due to firebug,

    a) I know that my data are posted in sbmt.php

    b) **I get no response back to display the error msg.**

I am validating 3 more forms (textareas only if it matters) using the exact same way and they are working fine!

Any suggestion on what may be wrong here?

Thank you