Displaying Windows Task Scheduler Tasks with PHP

In building Dante, my task scheduler application, I have come across quite a bit of information about dealing with COM through PHP.  Once I gained a simple understanding of the COM system in PHP I learned the rest from Win32 and COM Development on MSDN.  I hope to share a bit of what I have learned.  The focus of Dante will be on Windows first. Later I want to be able to support UNIX systems too, so I will keep that in mind as I build my class. As I never have enjoyed VBS so implementing it in PHP will make for a much more enjoyable experience scripting.  My intention is to take everything I work on and bringing it into my framework.  Hopefully you find this information helpful, or if you just want to use this functionality check out the Crossley Framework.  Dante PHP Job Scheduler will have a project page soon, so stay tuned.

So the first piece of Dante that will always be important is displaying the tasks that are scheduled to run.  A Factory method is used with COM objects in PHP or VBS.  As discussed earlier, it is called COM() in PHP.  A quick trip over to the Task Scheduler MSDN refrence tells us there are four high-level steps we need to take.

1. Create a TaskService object (using COM())
2. Get a task folder (tasks are organized into a directory tree)
3. Get the collection of tasks from that folder
4. Count, Iterate and perform any other operations on the tasks.

These are mostly obvious.  So the first thing I need to do is checkout the TaskService object.  This will be the means for managing registered tasks.  From the documentation you can see that the TaskService object has a limited number of methods: Connect(), NewTask(), GetFolder() and GetRunningTasks().  My goal  will be to completely obfusticate the functionality passing these calls onto the instance.

On the simplest level I want to be able to call my class like this:

$oTaskService = new X_Scheduler_Win_Service();
$aTasks = $oTaskService->getTasks();
print "<ul>";
foreach ($aTasks as $oTask)
{
print "<li><b>{$oTask->sName}</b>
print "{$oTask->sPath} : {$oTask->sNextRunTime}</li>"
}
print "</ul>";

I will try to place all the connect logic in the constructor.  I will allow for D-COM pass through, but I am not going to be worried about making it work this go arround.   If you decide to experiment with it, you should know that it needs to be enabled in your php.ini.  D-COM basically allows you to connect to a different server to run COM.

One of your best friends is com_print_typeinfo().  However it can leave you high and dry if the COM object doesn’t support the introspection from com_print_typeinfo().  Sadly this seems to be the case with ‘IRegisteredTaskCollection’.  In this case you just have to trust the MSDN documentation.  If I had one wish for PHP on Windows it would be that this function be improved.  The other qualm I have is that it outputs directly and does not return a string.  I think it should at least have the option like print_r().

So lets take the first step and get a count of tasks.

$oSchedule = new COM("Schedule.Service");
$oSchedule->Connect();
$oFolder = $oSchedule->GetFolder("\");
$oCollection = $oFolder->GetTasks(0);
print "Count: " . $oCollection->Count . "n";

The first two lines you will see repeated constantly when dealing with COM.  We are basically getting an instance of the TaskService object and connecting to the running service.

Then, since the schedule is organized in a directory tree style folder structure we need to get the folder we are going to deal with.  Here we get the root folder, but later we will get organized into our own folder.  Just like dealing with the file syste, tasks concealed within folders are not visible from the parent folder.  The TaskService object also offers the following methods and properties:

TaskService methods:

TaskService properties:

The parameter passed to GetTasks() signifies what type of tasks to list. To list all the normal tasks we pass ’0′ (zero).  We can list hidden tasks by passing ’1′.

Once we have a collection we can get the count from the ‘Count’ attribute.

The next step I want to take is to turn the collection into a native PHP array.  At this point it is good to take note that the first item in this collection is not 0 as with normal PHP arrays.  The first item is thus ’1′.  Taking this into consideration we form a for loop:

$aTasks = array();
for ($i = 1; $i <= $iCollectionCount; $i++)
{
$aTasks[] = $oCollection ->Item($i);
}

The collection is also iterable in a foreach loop:

$aTasks = array();
foreach ($oTaskCollection as $oItem)
{
$aTasks[] = $oItem;
}

You may ask why I am adding a loop if it is already iterable.  The plan here is to end up with a totally native concrete object.  There may be a way to cast returned objects to PHP classes, but we will save that for later

Now lets take a look at the RegisteredTask object.  One property that seems to have great potential is ‘XML’.  Here are the RegisteredTask Properties:

Notice that all the properties we mentioned before are present.  Observing the methods of this object we see everything we may ever want to do with a task:

In building  my class, the instanciation and connection is done in the constructor with the option to pass through the additional options.  The TaskService object also offers a connect in addition to the COM connect methods.  This allows us to use additional user credentials without going the D-COM route.  Thus, I will create a method to neatly take advantage of reconnecting with a different username and password.  Then I will stub out a Task class that we will later use for convience methods.

Next: Scheduling a Task in Windows Task Scheudler with PHP