hmm i thought some developer would at least look at this issue ...
but anyway, today i had some time to debug this ..
as stated before it comes down to rcube_session.php
but the culprit is actually the used array_merge.
php manual says for array_merge:
http://uk.php.net/array_mergeIf the input arrays have the same string keys, then the later value for that key will overwrite the previous one. If, however, the arrays contain numeric keys, the later value will not overwrite the original value, but will be appended.
If all of the arrays contain only numeric keys, the resulting array is given incrementing keys starting from zero.
for some reason rcube creates empty array items (such as array(1=>,2=>,3=>)
in the session when the user accesses lists. (that's what it seems like at least) and array_merge duplicates these empty array items until there is no memory left
my easy solution was to replace the following:
./program/include/rcube_session.php
around line 108:
replace
$newvars = $this->serialize(array_merge(
(array)$a_oldvars, (array)$this->unserialize($vars)));
with
$newvars = $this->serialize( (array)((array)$a_oldvars+(array)$this->unserialize($vars)) );
no more duplication in the session spares the memory and the user can actually use the webmail.