Description:
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Storing a closure in APC silently fails (or stores null), and retrieving it later 
ends up returning null which causes fun problems like "Function name must be a 
string in ..."

Use case: It's common to store app configuration in APC, and some configuration 
includes closures. If you have a closure in your config array and attempt to store 
it in APC, there are no warnings or errors; yet when fetching this value from APC 
it returns null.


Probably related to https://bugs.php.net/bug.php?id=63021 (I don't know if APC 
uses serialize or var_export, but it's the same general problem)

Test script:
---------------
$fn = function() { return 1; } ;

$ret = apc_store('test', $fn);

var_dump($ret); // NULL

$fetched = apc_fetch('test');

var_dump($fetched); // NULL

Expected result:
----------------
either a)

apc_store('key', $value_containing_closure) will throw an exception or issue some 
sort of warning (PHP notice?)

More accurately, var_export/serialize on a closure should probably handle this

or b)

it works (closures can be serialized/exported)