Insert Array Value to Mysql/Php

Hi guys, please see below.

$a=array (100,200,300,x,y,z);

I want this six data to be insert in mysql table in six row, repeatedly.

mysql-tabel

ID--SIZE
1--100
2--200
3--300
4--X
5--Y
6--Z
7--100
8--200
9--300
10--X
11--Y
12--Z
------
------
------

How can I do this?