Two times!

Custom Error Handler -- Warning/Notice
An error has occurred on 31 line in the /usr/local/apache/htdocs/hughs-book/2nd-edition/examples/ch12/example.12-1.php file.
The error is a "Missing argument 1 for double()" (error #2).
Here's some context information:
Array
(
    [number] => 
)
Two times ten is: 0