No need to use second ajax function, you can get it back on success inside a function, another issue here is you don't know when the first ajax call finished, then, even if you use SESSION you may not get it within second AJAX call.
SO, I recommend using one AJAX call and get the value with success.
example: in first ajax call
$.ajax({
url: 'ajax.php', //This is the current doc
type: "POST",
data: ({name: 145}),
success: function(data){
console.log(data);
alert(data);
//or if the data is JSON
var jdata = jQuery.parseJSON(data);
}
});