Ok, I am trying to make it available for people to post on my website, and I'm having difficulties with the most ridiculous thing in the world!

So I added A form for people to type in their news... and i have an input button, and then some php so the but puts the news into my database

but when i open my browser it says undefined index post on line 5; so here is my code in php calling for a post:
if ($_POST['post'])

And The Button Is Set Up Like This:
<input type='submit' name='post' value='post this news' href='csbpost.php'>

Can Anyone Help... And thanks for taking the time to read this!