You should say to PDO, that you want only an associative array or a numbered array:
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_ASSOC))
to get an associative array or
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_NUM))
to get an array indexed by the column number
from PDOStatement::fetch
fetch_style
Controls how the next row will be returned to the caller.
This value must be one of the PDO::FETCH_* constants, defaulting to
value of PDO::ATTR_DEFAULT_FETCH_MODE (which defaults to
PDO::FETCH_BOTH).PDO::FETCH_ASSOC: returns an array indexed by column name as returned
in your result setPDO::FETCH_BOTH (default): returns an array indexed by both column
name and 0-indexed column number as returned in your result set