If you're smart enough to find out that you an disable memory_limit by 
setting it to -1, you should are smart enough to see that this error 
message bogus, like you did.

The problem is that we need to rewrite parts of the PHP setting 
detection only to deal with this single case, and it's not worth it.

watch the message test.php gave me. it says "Current value of 
memory_limit: -1". I'd say, test.php should recognize that 
memory_limit = -1 is the same as a disabled memory_limit

Then you haven't changed the memory limit correctly, or didn't restart 
PHP, or something else related to your PHP configuration (not Horde).   
Horde's test.php displays your settings as reported to it by PHP.

After reading PHP-Help, I found this:

memory_limit integer

This sets the maximum amount of memory in bytes that a script is 
allowed to allocate. [...]. Note that you have to set it to -1 if you 
don't want any limit for your memory.



So i've added the line

php_admin_value memory_limit -1

to my virtual host for horde. The limit is actually set to -1, 
however, horde test.php would still print:

memory_limit disabled: No

If PHP's internal memory limit is turned on and if not set high enough 
Horde will not be able to handle large data items (e.g. large mail 
attachments in IMP). If possible, you should disable the PHP memory 
limit by recompiling PHP without the "--enable-memory-limit" flag. If 
this is not possible, then you should set the value of memory_limit in 
php.ini to a sufficiently high value (Current value of memory_limit: 
-1).



instead of just "Yes"