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<?php class Test { public function foo() { $x = ['foo', 'bar']; // The actual operation isn't important, just need to do something to turn the literal // strings into refcounted strings var_dump(__LINE__); debug_zval_dump($x[0]); $y = array_map(function($it) { return $it.$it; }, $x); var_dump(__LINE__); debug_zval_dump($x[0]); debug_zval_dump($y[0]); return array_unique($y, SORT_STRING); } } $result = (new Test())->foo(); var_dump(__LINE__); debug_zval_dump($result[0]); debug_zval_dump($result[1]); var_dump($result);
Output for 5.6.0 - 5.6.40, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.28, 7.4.0 - 7.4.16, 8.0.0 - 8.0.3
int(10) string(3) "foo" refcount(2) int(13) string(3) "foo" refcount(2) string(6) "foofoo" refcount(2) int(21) string(6) "foofoo" refcount(2) string(6) "barbar" refcount(2) array(2) { [0]=> string(6) "foofoo" [1]=> string(6) "barbar" }
Output for 7.0.0 - 7.0.33
int(10) string(3) "foo" refcount(3) int(13) string(3) "foo" refcount(3) string(6) "foofoo" refcount(2) int(21) string(6) "foofoo" refcount(2) string(6) "barbar" refcount(2) array(2) { [0]=> string(6) "foofoo" [1]=> string(6) "barbar" }