On PHPCodeBase.com there's a recent post looking at a handy file system function that you can use to search directories simpler than a usual opendir/readdir method - glob.

Are you guys still using opendir() function to read the the files from the folder in PHP? Luckily PHP have the glob() function which perform this task very faster and smarter.

He compares an example of the opendir/readdir method to a few line replacement with glob, both searching the same directory for files. He looks at the arguments you can pass into glob - the path to search and a flag that adds special handling to the method (like turning off sorting, modifying the regular expression handling and stopping on errors).