If I have a block of PHP code in pre tags using the WP-syntax, any variant of
fclose() in a post will cause a total site crash (specifically, I get a 503 error). Removing just those lines fixes the problem (this is within a long chunk of PHP code).
I don't know whether this is an outshoot of WordPress freaking out that I have
fclose() in a post, or if--god forbid--that code is actually executing (that seems fantastically unlikely, of course), or if it's something with WP-syntax itself or its parser.
I've got a lot of stuff to finish on this site, so I haven't started digging too deeply on that 503 error. But I did verify that it was those lines of PHP in a post.