If the element to be pushed onto the end of array is an array you will receive the following error message: 

Unknown Error, value: [8] Array to string conversion

I tried both: (and works, but with the warning message)

            $aRol = array( $row[0], $row[1], $row[2] );
            $aRoles[] = $aRol;

and 
            array_push( $aRoles, $aRol);

The correct way:

            $cUnRol = implode("(",array( $row[0], $row[1], $row[2] ) ); 
            array_push( $aRoles, $cUnRol ); 

thanks.