> For the complete documentation index, see [llms.txt](https://docs.neuron-ai.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.neuron-ai.dev/v2/workflow/multi-step-workflow.md).

# Multi Step Workflow

Multiple steps are created by defining custom events that can be emitted by nodes and trigger other nodes. Let's define a simple 3-step workflow.

### Custom Events

We define two custom events, `FirstEvent` and `SecondEvent`. These classes can have any names and properties, but must implement `Event`:

```php
namespace App\Neuron;

class FirstEvent implements Event 
{
    public function __construct(protected string $firstMsg){}
}

class SecondEvent implements Event 
{
    public function __construct(protected string $secondMsg){}
}
```

### Defining the workflow

Now we define the workflow itself. We do this by defining the input and output types on each node.

{% tabs %}
{% tab title="Unix" %}

```bash
./vendor/bin/neuron make:node App\\Neuron\\InitialNode

./vendor/bin/neuron make:node App\\Neuron\\NodeOne

./vendor/bin/neuron make:node App\\Neuron\\NodeTwo
```

{% endtab %}

{% tab title="Windows" %}

```powershell
.\vendor\bin\neuron make:node App\Neuron\InitialNode

.\vendor\bin\neuron make:node App\Neuron\NodeOne

.\vendor\bin\neuron make:node App\Neuron\NodeTwo
```

{% endtab %}
{% endtabs %}

Here is the minimal implementation for the purpose of this demo:

```php
namespace App\Neuron;

use NeuronAI\Workflow\Node;
use NeuronAI\Workflow\StartEvent;
use NeuronAI\Workflow\StopEvent;

// Gets the StartEvent and returns FirstEvent
class InitialNode extends Node
{
    public function __invoke(StartEvent $event, WorkflowState $state): FirstEvent
    {
        echo "\n- Handling StartEvent";
        
        return new FirstEvent("InitialNode complete");
    }
}

// Takes FirstEvent as input and returns SecondEvent
class NodeOne extends Node
{
    public function __invoke(FirstEvent $event, WorkflowState $state): SecondEvent
    {
        echo "\n- ".$event->firstMsg;
        
        return new SecondEvent("NodeOne complete");
    }
}

// Takes SecondEvent as input and returns StopEvent
class NodeTwo extends Node
{
    public function __invoke(SecondEvent $event, WorkflowState $state): StopEvent
    {
        echo "\n- ".$event->secondMsg;
        
        echo "\n- NodeTwo complete";
        
        return new StopEvent();
    }
}
```

Define the Workflow attaching the nodes:

```php
use NeuronAI\Workflow\Workflow;

$handler = Workflow::make()
    ->addNodes([
        new InitialNode(),
        new NodeOne(),
        new NodeTwo(),
    ])
    ->start();

/*
 * Run the workflow
 */
$handler->getResult();
```

The full output will be:

```
- Handling StartEvent
- InitialNode complete
- NodeOne complete
- NodeTwo complete
```

<figure><img src="/files/69WmObamPhcKyXcMxTRI" alt=""><figcaption></figcaption></figure>

Of course there is still not much point to a workflow if you just run through it from beginning to end! Let's do some branching and looping.

### Monitoring & Debugging

Before moving into the Workflow creation process, we recommend having the monitoring system in place. It could make the learning curve of how Workflow works much easier. The best way to monitoring Workflow is with [Inspector](https://inspector.dev/).

After you sign up at the link above, make sure to set the `INSPECTOR_INGESTION_KEY` variable in the application environment file to monitoring Workflow execution:

{% code title=".env" %}

```
INSPECTOR_INGESTION_KEY=nwse877auxxxxxxxxxxxxxxxxxxxxxxxxxxxx
```

{% endcode %}