Create Your Own PHP/AMF Data Service For Flex

This is a quick and short tutorial on how to create your own data services for flex to read. Also, note that in this tutorial we will be focussing on what a PHP Developer would be doing and not what a Flex Developer would do, we are not going to go over setting up data services or Flex, we are just going to be writing out classes.

Classes

The class is a rather simple thing to write out when focussing on creating an object that flex will be able to easily read. The trick to creating proper services is knowing what flex can do with your functions and your class.

The first thing to know is that flex is not going to be passing any values into the class and the class is not going to behave in a similar fashion to flex. This means that everything you do needs to operate on a function level.

The Construct

The construct is going to allow you to store information into the classes variables such as anything else and thus it is a good place to initialize and store a connection.

There isn’t a standard class declaration line within Flex and thus you cannot simply pass arguments through the parameters of the class.

The construct should look like this:

1
2
3
4
5
6

public function __construct()
{
    session_start();
    $this->connection = new mysqli('localhost','root','password','databasename');
 
}

Function Error Returns

Remember that the front end development team is going to need to know how to handle every situation of data that they receive and they will need to handle any scenario. Because of this you are going to need to return a status and message within the object in case anything goes wrong. A common standard is to simply store a boolean of if it worked as the first value returned. If the boolean is a false value then we know that the second object in the array is going to be an error message or an error code letting the front end know what went wrong.

Function Arguments

When setting up your arguments in the parameters of a function you are going to need to break away from pre setting the value of the argument with:

1

public function getMeta($metaName, $metaType = "video"){}

Values that are pre set in PHP do not show up in flex as an optional parameter.

Returning the Object

When using PHP/AMF as a data service it is good likely that you will need to return some rather complex objects to the front end team. The best way to pass data and allow them to use it is to store the information within an multi-dimensional array.

This means that when you use something like a prepared statement, you are going to need to handle the data and not just throw it back in a PHP array. If you throw back an unhandled mysqli array the front end team may kill you, especially if you have joins within your connection. This will force them to recreate an object from a singular one dimensional array.

Example of a custom Data Service.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35

public function pullVideoFromUser($userNid)
    {
        //Query the database and pull video information
        $sql = "SELECT t.name tour_name, t.tour_nid video_nid, tm.created tour_created, tm.modified tour_modified, tm.viewcount tour_viewcount
            FROM tbl_user_video ut
            INNER JOIN tbl_video t ON ut.video_nid = t.video_nid
            INNER JOIN tbl_video_meta tm ON tm.video_nid = tu.video_nid
            WHERE u.user_nid = ?";
 
        $videoReturn = array();
        if($stmt = $this->connect->prepare($sql))
        {
            $stmt->bind_param('i', $userNid);
            $stmt->execute();
            $stmt->store_results();
            if($stmt->num_rows >= 1)
            {
                $stmt->bind_results($key, $name, $nid, $created, $modified, $viewcount);
                while($stmt->fetch())
                {
                    //create an object holding the appropriate information
                    $videoReturn[] = array('status' => 1,'key' =>$key, 'name' => $name, 'nid' => $nid, 'created' => $created, 'modified' => $modified, 'viewcount' => $viewcount);
                }
            }else{
                //Store a status of false and return an error message within the object.
		$videoReturn[] = array('status' => 0, 'message' => 'There was an issue returning the video.')
	    }
        }else{
            //Store a status of false and return an error message within the object.
	    $videoReturn[] = array('status' => 0, 'message' => $this->connection->error);
	}
        //return the object
        return $videoReturn;
 
    }