Help with simple PHP/MySQL?

[Nathan]

I'll start with the PHP/MySQL error I'm getting:


Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in /hermes/bosweb/web161/b1610/ipg.teklyscom/news/resources/func/blog.php on line 71

On blog.php I have:
function get_categories($id = null) {
$categories = array();
$query = mysql_query("SELECT 'id', 'name' FROM 'categories'");
while ($row = mysql_fetch_assoc($query)) { #THIS IS LINE 71
$categories[] = $row;
}
return $categories;
}


What am I doing wrong? Thanks in advance.