gistfile1.php

// the model /////////////////////////////////////////////////////////////////////

class Post extends \yii\db\ActiveRecord
{
    /**
     * @inheritdoc
     */
    public static function tableName()
    {
        return 'item';
    }

    /**
     * @inheritdoc
     */
    public function rules()
    {
    	return [
    	  // The RelatedWorkflowValidator is in charge of validating status_ex transition
    	  // depending on transition occuring on the primary workflow (status attribute)
    	  
    		['status_ex',RelatedWorkflowValidator::className()],
    	];
    }    
    /**
     * (non-PHPdoc)
     * @see \yii\base\Component::behaviors()
     */
    public function behaviors()
    {
    	return [
    	  // Primary workflow
    		'w1' =>[
    			'class' => \raoul2000\workflow\base\SimpleWorkflowBehavior::className(),
    			'statusAttribute' => 'status',
    			'defaultWorkflowId' => 'PostWorkflow1'
    		],    		
    		// Secondary workflow
    		'w2' => [
    			'class' => \raoul2000\workflow\base\SimpleWorkflowBehavior::className(),
    			'statusAttribute' => 'status_ex',
    			'defaultWorkflowId' => 'PostWorkflow2'
    		]
    	];
    }
}

// PostWorkflow1 definition /////////////////////////////////////////////////////////////////////

class PostWorkflow1 implements IWorkflowDefinitionProvider 
{
    public function getDefinition() {
        return [ 
            'initialStatusId' => 'draft',
            'status' => [
                'draft' => [
                    'transition' => ['correction']
                ],
                'correction' => [
                    'transition' => ['draft','ready']
                ],
                'ready' => [
                    'transition' => ['draft', 'correction', 'published']
                ],
                'published' => [
                    'transition' => ['ready', 'archived']
                ],
                'archived' => [
                    'transition' => ['ready']
                ]
            ]
        ];
    }
}

// PostWorkflow2 definition /////////////////////////////////////////////////////////////////////

class PostWorkflow2 implements IWorkflowDefinitionProvider 
{
    public function getDefinition() {
        return [ 
            'initialStatusId' => 'success',
            'status' => [
                'success' => [
                    'transition' => ['onHold']
                ],
                'onHold' => [
                    'transition' => ['success']
                ],
            ]
        ];
    }
}

// The Standalone Validator class /////////////////////////////////////////////////////////////////////

use yii\validators\Validator;
use raoul2000\workflow\validation\WorkflowScenario;

class RelatedWorkflowValidator extends Validator
{
	
	private $constraint;

	/**
	 * Set constraint array where keys are scenario for the secondary workflow, and
	 * values are array of scenario for the primary workflow that allow secondary transition. 
	 * If value is TRUE, the secondary transition is allowed.
	 * 
	 * @see \yii\validators\Validator::init()
	 */
	public function init()
	{
		parent::init();
		
		$this->constraint =  [
			// model can enter into secondary workflow no matter what is the primary workflow transition	
			WorkflowScenario::enterWorkflow('Post4Workflow2') => true, 
		
			WorkflowScenario::changeStatus('Post4Workflow2/success', 'Post4Workflow2/onHold') => [
				WorkflowScenario::changeStatus('Post4Workflow1/draft', 'Post4Workflow1/correction'),
				WorkflowScenario::changeStatus('Post4Workflow1/ready', 'Post4Workflow1/draft')
			],
		
			WorkflowScenario::changeStatus('Post4Workflow2/onHold', 'Post4Workflow2/success') => [
				WorkflowScenario::changeStatus('Post4Workflow1/correction', 'Post4Workflow1/ready')
			]
		];
	}	
	/**
	 * Perform validation.
	 * WARNING : primary and secondary status attribute names are hard coded (to change if needed)
	 * 
	 * @see \yii\validators\Validator::validateAttribute()
	 */
	public function validateAttribute($model, $attribute)
	{

		$w2scenarios=null;
		$w1scenarios=null;
		try {
			 
			list(,$w2scenarios) = $model->getBehavior('w2')->_createTransitionItems($model->status_ex, true, false);
			if( $w2scenarios == null) {
				return; // no pending transition for w2 : validation succeeds
			}
		} catch (Exception $e) {
			$this->addError($attribute, 'invalid transition on secondary workflow');
			return;
		}
		
		try {
			list(,$w1scenarios) = $model->getBehavior('w1')->_createTransitionItems($model->status, true, false);
		} catch (Exception $e) {
			$this->addError($attribute, 'invalid transition on primary workflow');
			return;
		}
		
		foreach ($w2scenarios as $w2sc) {
			if (isset( $this->constraint[$w2sc])) {
				if( $this->constraint[$w2sc] === true) {
					return;
				}elseif($w1scenarios === null &&  in_array($w1scenarios, $this->constraint[$w2sc])) {
					return;
				}else {
					foreach ($w1scenarios as $w1sc) {
						if( in_array($w1sc,$this->constraint[$w2sc])) {
							return;
						}
					}
				}
			}
		}
		
		// the constraint array does not contain secondary AND related primary transition
		// for the current model.
		
		$msgInfo= implode(', ',$w2scenarios);
		$this->addError($attribute, 'constraint failed : '. $msgInfo);		
	}
}

Thank you so much for your help , I'll test it now and see what I can do. I will update you soon

Do you know how to get defaultWorkflowId from controller ?

            'w1' =>[
                'class' => \raoul2000\workflow\base\SimpleWorkflowBehavior::className(),
                'statusAttribute' => 'status',
                'defaultWorkflowId' => 'PostWorkflow1'
            ],

I already got it , thank you , i'll update you soon