set_query（）中的行说明[关闭]

I need help to understand the following code. What I want to know is the code line in the set_query($data,$limit_enable). If any help regarding the matter would be highly appreciated.

function get_data($data){

    $out = array();
    $this->set_query($data,$limt_enabled);
    //some code
}

function set_query($data,$limit_enable){

    $data['selection'] =  isset($data['selection'])? $data['selection']: 'task_master.staff_id,staff.full_name,creator_staff.full_name AS creator' ;
    //some code
 }

Actually $this->set_query($data,$limt_enabled); is calling the set_query() method of this same class and set_query() has one ternary expression which is

$data['selection'] =  isset($data['selection'])? $data['selection']: 'task_master.staff_id,staff.full_name,creator_staff.full_name AS creator' ;

It means

if( isset($data['selection']) )
{
    $data['selection'] = $data['selection'];
}
else
{
    $data['selection'] = 'task_master.staff_id,staff.full_name,creator_staff.full_name AS creator'
}

I'm not sure from which framework you have got it but it looks like that, if already $data['selection'] is not set for selection from table then set the selection criterion something like

select task_master.staff_id, staff.full_name, creator_staff.full_name

Which is actually going to be used for selecting some table fields and these are

 staff_id field from table `task_master
 full_name field from table `staff
 full_name field from table `creator_staff

Also it's setting an alias for this selection AS creator.