---
description: How to create the first workflow with a single node
title: Single Step Workflow
---

# Single Step Workflow

### Create a Workflow

A workflow is usually implemented as a class that inherits from Workflow. The class can define an arbitrary number of nodes, each of which is a class that extens `NeuronAI\Workflow\Node`.

First, let's create the MyWorkflow class:



### Unix

```bash
php vendor/bin/neuron make:workflow App\\Neuron\\MyAgent
```



### Windows

```powershell
php .\vendor\bin\neuron make:workflow App\Neuron\MyWorkflow
```



Here is the simplest possible workflow:

```php
namespace App\Neuron;

use NeuronAI\Workflow\Workflow;

class MyAgent extends Workflow
\{
    protected function nodes(): array
    \{
        return [
            new InitialNode(),
        ];
    \}
\}
```

Now let's create the node:



### Unix

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



### Windows

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



A Node is an invokable class to handle an incoming event, and return another event:

```php
namespace App\Neuron;

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

class InitialNode extends Node
\{
    public function __invoke(StartEvent $event, WorkflowState $state): StopEvent
    \{
        $state->set('answer', 'Hello World!');
        
        return new StopEvent();
    \}
\}
```

This will print "Hello World!" to the console:

```php
$finalState = MyWorkflow::make()->start()->getResult();

echo $finalState->get('answer'); // Print Hello World!
```

In this code we:

* Define a class MyWorkflow that inherits from Workflow
* Define a Node implementing the \_\_invoke method
* The step takes an event as input, $event, which is an instance of StartEvent
* The Node adds a value to the state and returns a StopEvent
* We create an instance of MyWorkflow 
* We start the workflow and get the result
* Print the result in the console

<figure><img src="../.gitbook/assets/workflow-single-step.png" alt="" /><figcaption></figcaption></figure>

### Type hint for events

The $event types (e.g. `StartEvent`) guide the Workflow execution. The expected return types of a node determine what node will be triggered next.

Event types are validated at compile time, so you will get an error message if for instance you return an event that is never consumed by another Node.

### Start and Stop events&#xD;

`StartEvent` and `StopEvent` are special events that are used to start and stop a workflow. The node that accepts a StartEvent will be triggered first by when you start the workflow. Returning a StopEvent will end the execution of the workflow and return the final state, even if other nodes remain un-executed.

### 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 more 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:


// .env

```
INSPECTOR_INGESTION_KEY=nwse877auxxxxxxxxxxxxxxxxxxxxxxxxxxxx
```