PHP workflows – ezComponents

Workflows are a useful tool to help manage business processes. In this post I take a look at the workflow engine of eZ components, which was developed by Sebastian Bergmann. In this post, I introduce the basics of the workflow engine, and will expand on it’s usage in future posts.

The first step is to download eZ components. At time of writing, the latest version is 2009.1.1 – eZ components can be downloaded from: http://www.ezcomponents.org/download

A workflow flows from node to node, sometimes branching conditionally, or splitting to parallel tasks. It flows from the startNode, to the endNode, unless the process is canceled at some point during execution. We start with a really basic workflow, which when started will simply write ‘Hello world’ to the screen.

lines 1-8

These lines just setup the autoloader
line 10

Creates a workflow with a name ‘Example 1’
lines 12-23
The ezcWorkflowServiceObject interface can be implemented to provide custom code that can be executed by a ezcWorkflowNodeAction once it is reached in the workflow. If execute() returns true, the workflow proceeds, else it is stalled.
line 25
Creates a action node, which will instance and execute the myServiceObject class when reached.
line 27-28
Defines step1 as the action node, linking it to the outNode of the workflows start, and linking it’s own outNode to the endNode of the workflow.
line 30-32
An execution object is created, the workflow assigned, and the execution is started.
line 34-38
Checks that the workflow is complete as we’d expect it to be

The output of this script is as follows:

We will now modify this example to be a little more personal. We will introduce an input node, which will stall the workflow execution until required input is acquired, and provided to the workflow. Once the input is provided, execution continues to an action node which instances a slightly modified service object, which says hello.

The code is very similar to the first example, so I’ll cover just the main differences below:

line 17
Accesses a variable called ‘name’ of the workflow
line 27-29
Creates an input node, which will take input from the application. In this instance it’s requiring a ‘name’ of type string.

line 33-35
Configuring the work flow
line 37-39
The details of this will be covered in my next post on the workflow component

Execution of the workflow is started in this example in much the same was as the previous example – however execution does not finish on the first call to $execution->start(). This is because of the input node requiring a ‘name’ before it can continue. In line 50, we ask the exeuction to resume, providing the name , at which point execution continues, prints hello, and then finishes. The output is as follows:

In a follow up post, I will show a more realistic use of workflows, and show a few more of the workflow components in action.

13 thoughts on “PHP workflows – ezComponents”

  1. Well, I guess it depends what you’re trying to integrate exactly 🙂

    I don’t though – because I’ve not really spend much time looking at Zend yet. What is it you’re trying to do out of interest?

  2. Ian, i live in Santa Fe, Argentina and actually i’m working as project leader in software development. I’ve seen your article (very interesting), but i’d like to have, as you’ve said, “more realistic use of workflow”.
    Thanks a lot for your time! (and apologise me for my bad english).

  3. I’ve managed to integrate it with Zend Framework 1.10+ like this way:

    1) put it in the libraryezc directory
    2) In Bootstrap.php
    protected function _initAutoload()
    {

    require_once ‘../library/ezc/Base/src/base.php’;

    $autoloader = Zend_Loader_Autoloader::getInstance();
    $autoloader->pushAutoloader(array(‘ezcBase’, ‘autoload’), ‘ezc’);
    return $autoloader;
    }

  4. Hello,

    I have two general problems with the understanding of the workflow-functionality:

    1.) If I have defined a general workflow (for example for publish an article after a review) – each posted article has actually start a new “instance” of my general publish-workflow. Is this right? Or how does I handle it when the same workflow is used for many different articles/data-sets? And how can I generate a “instance” of a general workflow?

    2.) How does the basis-application have to work with the workflow-component? If in the publish-process an email has to send to the person who has to review the article – where has the code to be placed for sending this email? Is it the right approach to send the email directly in the workflow, for example in the execute-method in a WorkflowServiceObject? Or does the sending of the email just placed in the application-code (after save an article or set the state of an article) and the status of the workflow has to set to the next node/level after sending the email?

    Thanks for an answer (and sorry for my bad english ;-))!

    Timo

  5. @Lula. Here is an easier way to integrate with ZF if you are using teh ZF Bootstrapper. This illustration assumes that the EZC lib is already off of one of your include paths. (I used the PEAR installer so /usr/share/pear is already in php include path.)

    Inside your bootstrap class, put the following;

    /**
    * Load the EZ Components library
    * Cannot be done via the autoloader application.ini config
    *
    */
    public function _initLoadEZC() {
    require_once ‘ezc/Base/base.php’;
    $autoloader = Zend_Loader_Autoloader::getInstance();
    $autoloader->pushAutoloader(array(‘ezcBase’, ‘autoload’), ‘ezc’);
    }

    That’s it.

  6. Very good article!
    I’m a cuban student at the University of the Informatics Sciences. I would like to know how can I integrate ezComponents with CodeIgniter framework. Thanks.

Leave a Reply

Your email address will not be published. Required fields are marked *