request in PhpMyAdmin works, with Laravel Query Builder, doesn't seem to work

I have a problem that I can't fix :

this request works in PHPMYADMIN

SELECT cronState.name, command.name, parameter.keyword, eventParameterValue.value
FROM cronState, commandInstance, command, eventParameterValue, parameter
WHERE cronState.id = commandInstance.cronState_id
AND commandInstance.command_id = command.id
AND eventParameterValue.commandInstance_id = commandInstance.id
AND eventParameterValue.parameter_id = parameter.id
AND cronState.id =32

it returns :

name    name            keyword     value   

on20    DigitalPinSet   State       1
on20    PwmPinSet       DutyCycle   20

and it's ALL I want.

LITTLE EDIT : I use an AJAX Request(with a state_name) to this method which should returns the query result.

Now, when I try to implement it with the Laravel Query Builder, it returns some errors.

My code:

    $cronState_id = DB::table('cronState')
        ->where('name', Input::get('state_name'))
        ->first();
    $cronEvent = DB::table('cronState')
        ->join('commandInstance', 'commandInstance.cronState_id', '=', 'cronState.id')
        ->join('command', 'commandInstance.command_id', '=', 'command.id')
        ->join('eventParameterValue', 'eventParameterValue.commandInstance_id', '=', 'commandInstance.id')
        ->join('eventParameterValue', 'eventParameterValue.parameter_id', '=', 'parameter.id')
        ->where('cronState.id', '=', $cronState_id->id)
        ->select('cronState.name', 'command.name', 'parameter.keyword', 'eventParameterValue.value');

foreach($cronEvent as $result){
        $ev =  $result['keyword'];
    }

return $ev;

The error for this code :

{"error":{"type":"ErrorException","message":"Undefined index: keyword","file":"/var/www/stage/app/controllers/EventController.php","line":48}}

if I change

foreach($cronEvent as $result){
        $ev =  $result['keyword'];
    }

return $ev;

to

return $cronEvent;

(just delete the foreach loop and rename the returning variable), I have this error :

{"error":{"type":"ErrorException","message":"Object of class Illuminate\Database\Query\Builder could not be converted to string","file":"/var/www/stage/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Response.php","line":361}}

So, how can access to my data in the object ? Maybe my Query Builder implementation doesn't works...

Thanks for any help !