NodeJS + Redis + HTTP Get

I'm currently getting data from my database by the way of PHP using Nodejs. The problem is that the script that I want to execute after grabbing datas is actually executing directly after the instance of my grabing function and I get everytime an error saying that my datas are undefined.

Here is my code :

var http = require('http'),
redis = require("redis");
client = redis.createClient();

        client.on("error", function (err) {
          console.log("Error " + err);
        });

        var sessionData;
        // Check if we have session create with sessionID gived before (hash)

        client.get('sessions:'+sessionId, function (err, result) {
            var resData;
            //Check if we have session with the session id 
            // If we have not execute function to get the data
            if(err || !result)
            {
                executefunction(get_sess_data,sessionId);
            }
            // If we have, get it from redis
            else
            {   
                resData = result;
                console.log(resData);
            }
            // settings session data with the result
            sessionData = JSON.parse(resData);
        });
// Execute function with sessionid as value

function executefunction(someFunction, value) {
  someFunction(value);
}
// Getting data from database (using script from Codeigniter)

var get_sess_data = function(response)
{
    var options = {
            host: 'www.example.dev',
            port: 80,
            path: '/index.php/user_session/decrypt?id='+sessionId
        };
    http.get(options, function(result) {
        result.on("data", function(chunk) {
            client.setex('sessions:'+sessionId, 21600, chunk.toString());

        }).on('error', function(e) {
            console.log("Got error: " + e.message);
        });
        result.end(response);
    });
};

FYI, I know the code to grab data is working because I can return them if I don't execute the following script "sessionData = JSON.parse(resData);" even if I place it in my if statement.

I'm stuck for hours on it. If anyone have an issue, let me know.