How do I return a proper success/error message for JQuery .ajax() using PHP?
<script type="text/javascript">
  $(function() {
    $("form#subsribe_form").submit(function() {
      var email = $("#email").val();

      $.ajax({
        url: "subscribe.php",
        type: "POST",
        data: {email: email},
        dataType: "json",
        success: function() {
          alert("Thank you for subscribing!");
        },
        error: function() {
          alert("There was an error. Try again please!");
        }
      });
      return false;
    });
  });
</script>

<?php
$user="username";
$password="password";
$database="database";

mysql_connect(localhost,$user,$password);
mysql_select_db($database) or die( "Unable to select database");

$senderEmail = isset( $_POST['email'] ) ? preg_replace( "/[^.-_@a-zA-Z0-9]/", "", $_POST['email'] ) : "";

if($senderEmail != "")
    $query = "INSERT INTO participants VALUES (CURDATE(),'".$senderEmail."')";
mysql_query($query);
mysql_close();

$response_array['status'] = 'success';

echo json_encode($response_array);
?>

header('Content-type: application/json');
    echo json_encode($response_array);

?>

data: {'email': email},

if(mysql_query($query))
    $response_array['status'] = 'success';
else
    $response_array['status'] = 'error';

success: function(data) {
      if(data.status == 'success')
          alert("Thank you for subscribing!");
      else if(data.status == 'error')
          alert("Error on query!");
    },

$results = array(
   'error' => false,
   'error_msg' => 'Everything A-OK',
   'data' => array(....results of request here ...)
);
echo json_encode($results);

if (!data.error) {
   ... got data, do something with it ...
} else {
   ... invoke error handler ...
}

error:function(x,e){
            if(x.status==0){
                alert('You are offline!!n Please Check Your Network.');
            }else if(x.status==404){
                alert('Requested URL not found.');
            }else if(x.status==500){
                alert('Internel Server Error.');
            }else if(e=='parsererror'){
                alert('Error.nParsing JSON Request failed.');
            }else if(e=='timeout'){
                alert('Request Time out.');
            }else {
                alert('Unknow Error.n'+x.responseText);
            }
        }