Description:
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Since PHP 7, an array_map on $GLOBALS returns an IS_INDIRECT zval instead of a value.

Test script:
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array_map(function($x) use (&$lastval) { $lastval = $x; }, $GLOBALS);

extract([], 0, $lastval); // for example, anything that will fail on an invalid type

// or for direct proof, giving unknown type
var_dump(gettype($lastval));

Expected result:
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NULL // on gettype

Actual result:
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Assertion failed: (0), function _convert_to_string, file /Users/Bob/php-src-X/Zend/zend_operators.c, line 585.
Abort trap: 6