Originally Posted by Salathe

There are any number of reasons why the author decided to use the error suppression operator. It is very quick and painless to write (just one extra character and all the noise goes away!), they may think that is the only way to keep the errors from popping up, they may not care about any tiny, tiny, tiny performance hit incurred when the line is called (perhaps only once or a few times per page-load for most uses), etc..