$mtime = @filemtime($masterFile); should detect if the file exists first.

Use case:

Deployment tools such as Capistrano create a new directory upon each deploy and then symlink to the latest deploy

for example current -> /var/www/website/releases/20110220101853/

Let's say we launch a new ec2 instance, which initiates a new deploy

current then points to a new dir, for example current -> /var/www/website/releases/20110220101860/

When the new instance is hit, the cache looks to a file that does not exist, and causes an error until we clear out the cache.

What it should do is, instead of just grabbing executing filemtime, is see if the file exists first. If the file does not exist, it should return false so the cache object repopulates it