Description:
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current() only works on variables; no longer on arrays 
returned from functions.

This also explains Bug #34424, which has been classified as 
Bogus.

Reproduce code:
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$x = current(explode(' ','a b'));
echo $x;

Expected result:
----------------
a

Actual result:
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Fatal error: Only variables can be passed by reference in ...

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However, the following DOES work as expected:

$a = current($x=&explode(" ","a b"));

This new behaviour breaks backward compatibility. Furthermore, 
it introduces continuity problems. In both cases, an array is 
passed to current(), only one time it is stored in a variable 
and the other time it isn't. This should not make a 
difference, because even a "temporary array" should have a 
current element.