$wpdb->insert – inserting multiple rows

How do I use $wpdb->insert to insert multiple rows. Here is my code.

for($i=0; $i<=$urlCount; $i++) {
   $stat = $wpdb->insert(
        'WP_URLS',
        array(
            'POSTID' => $post->ID,
            'URL' =>   $_POST['url'.$i]
        )
    );
}

This code works only for the first insert (ie, when $i = 0 , when value is url_0 ). Sometimes the URL count will be more than 100 and sometimes it will be zero. So instead of writing the code for 100 times, I just want to have a simple loop that works for any number of records. Thats the reason I went for loop.

Thank you for the help.

The table structure is

CREATE TABLE WP_URLS (
   POSTID BIGINT NOT NULL,
   URL VARCHAR(254)
);