JQuery :: How To Get Ajax Response Data To Outside Callback Function

I have Javascript code that looks like this:
var data1;
$.post('save_search.php', formData, function(data) {
data1 = data;
});
jsonData = eval('(' + data1 + ')');
if (jsonData.return_status.search("successful") > -1)
$('#msg_div').html("<font color=red>Search was saved</font>");
else
$('#msg_div').html("<font color=red>Search was not saved. Try saving again.</font>");
"data1" comes up as undefined in the statement
jsonData = eval('(' + data1 + ')');

Even though "data" is a perfectly correct JSON string *inside* the callback function! I can put the eval statement inside the callback function and it will form a good JSON object, like this:
jsonData = eval('(' + data + ')');
I'm simply trying to get my Ajax response data to the outside of my callback function so I can use it in other Javascript code. I've never seen an ordinary function behave this way.