Use JSON to transfer data types (arrays and objects) between client and server.
In PHP:
In JavaScript:
PHP:
echo json_encode($id_numbers);
JavaScript:
id_numbers = JSON.parse(msg);
As Wolfgang mentioned, you can give a fourth parameter to jQuery to automatically decode JSON for you.
id_numbers = new Array();
$.ajax({
url:"Example.php",
type:"POST",
success:function(msg){
id_numbers = msg;
},
dataType:"json"
});