ext/standard/array.c: add tests when extracting negative keys

ext/standard/tests/array/extract_negative_keys.phpt

@@ -0,0 +1,31 @@
+--TEST--
+extract() with negative keys
+--FILE--
+<?php
+$a = [-5 => 'hello', 'world', 2 => 'positive', 'check' => 'extracted'];
+
+function foo(array $a) {
+	extract($a, EXTR_PREFIX_ALL, 'prefix');
+	var_dump(get_defined_vars());
+}
+
+foo($a);
+?>
+--EXPECT--
+array(3) {
+  ["a"]=>
+  array(4) {
+    [-5]=>
+    string(5) "hello"
+    [-4]=>
+    string(5) "world"
+    [2]=>
+    string(8) "positive"
+    ["check"]=>
+    string(9) "extracted"
+  }
+  ["prefix_2"]=>
+  string(8) "positive"
+  ["prefix_check"]=>
+  string(9) "extracted"
+}

ext/standard/tests/array/extract_negative_keys2.phpt

@@ -0,0 +1,11 @@
+--TEST--
+extract() with negative keys
+--FILE--
+<?php
+
+$arr = [-1 => "foo"];
+var_dump(extract($arr, EXTR_PREFIX_ALL | EXTR_REFS, "prefix"));
+
+?>
+--EXPECT--
+int(0)