Illuminate\Database\Query\Builder::getConnection PHP Method

    public function getConnection()
    {
        return $this->connection;
    }

 /**
  * Process an "insert get ID" query.
  *
  * @param \Illuminate\Database\Query\Builder $query        	
  * @param string $sql        	
  * @param array $values        	
  * @param string $sequence        	
  * @return int
  */
 public function processInsertGetId(Builder $query, $sql, $values, $sequence = null)
 {
     $results = $query->getConnection()->selectFromWriteConnection($sql, $values);
     $sequence = $sequence ?: 'id';
     $result = (array) $results[0];
     $id = $result[$sequence];
     return is_numeric($id) ? (int) $id : $id;
 }