Lots of functionality gets added to PHP all the time, and yet few people seem to be taking advantage of it. How would you, for example, read the contents of a file into a string? Like this?
If so, you are using code that was considered very fast before PHP 4.3 was released. However, in PHP 4.3 a new function was introduced called file_get_contents(), that takes a filename as its first parameter and returns as a string the entire contents of the file. It is very fast as it is very optimised, and neatly solves a problem that people have had to implement for themselves.
If you have not done so recently, take a good look through the PHP manual to see what is changed - lots of functions were added in 4.3, and many more in 5.0 so make sure you give your scripts a freshen up to take advantage of the latest features.