I dont think it works using an array directly and trying to insert the values into mysql, not sure tho!
the implode idea is probably best as shown in the script below:
<?php
// our array of fruit
$fruit = array('apple', 'mango', 'grapes', 'plum');
// use implode() function to join all array element values together to form one string
$joinedString = implode(",", $fruit);
// update or insert into your mysql table using $joinedString as the variable
?>
of course as I am sure you know, if you need the array back you can easily use the explode() function.