Hi, im trying to insert into a db table 'blog_it '

Ive declared values using:

PHP Code:
$lang $_GET['lang'];
$mdb "blog_";
$mdbf $mdb $lang
..and insert using:
PHP Code:
    $query "
INSERT INTO "
.$mdbf." (..... 
..however i get an error that 'blog_' can't be found (without the 'it')....ive echo $mdbf on the page and the full value is shown

...what i doing obviously wrong?...thanks in advance