Fatal error: Call to undefined function ceil() in

[dll1024]

im using WordPress 3.5 RC1 in windows localhost with xampp 3.1.0
2 times i see this error:

Fatal error: Call to undefined function ceil() in C:\xampp\htdocs\mysite\wordpress\wp-includes\pluggable.php on line 1234

first while i go to disable a plugin
second when i want to create a user
in both, i press back, and do it again, and no problem occured!

FWIW: Hard to see this as a WordPress core bug. ceil() is a core PHP function. The only way to get that error would be if ceil() was a forbidden function in php.ini.

Works for me, on Windows, but not using xampp.

What knutsp said.

There are more than 10 instances of ceil() in core. It's called via check_admin_referer() on virtually every screen in the admin.

If it sporadically fails in some cases and works on a second attempt, it's probably insufficient memory or some other configuration issue.

Please try the support forums for troubleshooting: ​http://wordpress.org/support/