Description:
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Currently in_array(NAN, [0,NAN, null]) results with false but I would expect true would be proper as NAN is indeed in haystack.

Test script:
---------------
<?PHP

echo "in_array(0, [0,NAN, null]) should result true" . PHP_EOL;
var_dump(in_array(0, [0,NAN, null]));

echo "in_array(null, [0,NAN, null]) should result true" . PHP_EOL;
var_dump(in_array(null, [0,NAN, null]));

echo "in_array(NAN, [0,NAN, null]) should result true but result false" . PHP_EOL;
var_dump(in_array(NAN, [0,NAN, null]));

Actual result:
--------------
xxxx:~/code/$ php x.php 
in_array(0, [0,NAN, null]) should result true
xxxx/x.php:4:
bool(true)
in_array(null, [0,NAN, null]) should result true
xxxx/x.php:7:
bool(true)
in_array(NAN, [0,NAN, null]) should result true but result false
xxxx/x.php:10:
bool(false)