You need to provide the right content type if you’re using JSON dataType. Before echo-ing the json, put the correct header.
<?php
header('Content-type: application/json');
echo json_encode($response_array);
?>
Additional fix, you should check whether the query succeed or not.
if(mysql_query($query)){
$response_array['status'] = 'success';
}else {
$response_array['status'] = 'error';
}
On the client side:
success: function(data) {
if(data.status == 'success'){
alert("Thank you for subscribing!");
}else if(data.status == 'error'){
alert("Error on query!");
}
},
Hope it helps.