You should take a look at www.php.net/error_log.
A word to the wise tho, Using email error reporting isnt always the cup of tea it sounds like to be. Here's why. Lets say somthing breaks, and you have 1000 hits to that page before you realize their's a problem, well that's 1000 emails that will be sitting in your mailbox, all for the same problem. Imagine 20,000 hits.
Its more realistic, and a real world approach to write these errors to a log file, and write a custom function to parse the rows from the log file, and send only 1 email, per error type.
HTH