framework/web/Controller.php
public function bindActionParams($action, $params)
    {
        if ($action instanceof InlineAction) {
            $method = new \ReflectionMethod($this, $action->actionMethod);
        } else {
            $method = new \ReflectionMethod($action, 'run');
        }

        $args = [];
        $missing = [];
        $actionParams = [];
        foreach ($method->getParameters() as $param) {
            $name = $param->getName();
            if (array_key_exists($name, $params)) {
                if ($param->isArray()) {
                    $args[] = $actionParams[$name] = (array) $params[$name];
                } elseif (!is_array($params[$name])) {
                    $args[] = $actionParams[$name] = $params[$name];
                } else {
                    throw new BadRequestHttpException(Yii::t('yii', 'Invalid data received for parameter "{param}".', [
                        'param' => $name,
                    ]));
                }
                unset($params[$name]);
            } elseif ($param->isDefaultValueAvailable()) {
                $args[] = $actionParams[$name] = $param->getDefaultValue();
            } else {
                $missing[] = $name;
            }
        }

        if (!empty($missing)) {
            throw new BadRequestHttpException(Yii::t('yii', 'Missing required parameters: {params}', [
                'params' => implode(', ', $missing),
            ]));
        }

        $this->actionParams = $actionParams;

        return $args;
    }
public function bindActionParams($action, $params)
    {
        if ($action instanceof InlineAction) {
            $method = new \ReflectionMethod($this, $action->actionMethod);
        } else {
            $method = new \ReflectionMethod($action, 'run');
        }

        $args = [];
        $missing = [];
        $actionParams = [];
        foreach ($method->getParameters() as $param) {
            $name = $param->getName();
            if (array_key_exists($name, $params)) {
                if ($param->isArray()) {
                    $args[] = $actionParams[$name] = (array) $params[$name];
                } elseif (!is_array($params[$name])) {
                    $args[] = $actionParams[$name] = $params[$name];
                } else {
                    throw new BadRequestHttpException(Yii::t('yii', 'Invalid data received for parameter "{param}".', [
                        'param' => $name,
                    ]));
                }
                unset($params[$name]);
            } elseif ($param->isDefaultValueAvailable()) {
                $args[] = $actionParams[$name] = $param->getDefaultValue();
            } else {
                $missing[] = $name;
            }
        }

        if (!empty($missing)) {
            throw new BadRequestHttpException(Yii::t('yii', 'Missing required parameters: {params}', [
                'params' => implode(', ', $missing),
            ]));
        }

        $this->actionParams = $actionParams;

        return $args;
    }
Binds the parameters to the action.
This method is invoked by [[\yii\base\Action]] when it begins to run with the given parameters.
This method will check the parameter names that the action requires and return
the provided parameters according to the requirement. If there is any missing parameter,
an exception will be thrown.
@param \yii\base\Action $action the action to be bound with parameters
@param array $params the parameters to be bound to the action
@return array the valid parameters that the action can run with.
@throws BadRequestHttpException if there are missing or invalid parameters.