test(lang): 添加 foreach 循环和 func_get_arg 函数测试用例

- 添加 foreachLoop-04.phpt 测试数组元素作为值的循环功能
- 添加 func_get_arg-001.phpt 测试 PHP7 中 func_get_arg 函数行为
- 添加 func_get_arg_variation.phpt 测试 func_get_arg 参数变化情况
- 验证 foreach 循环中数组元素赋值的预期输出结果
- 验证 func_get_arg 函数在不同参数位置下的异常处理

tests/core/lang/foreachLoop-004.phpt

@@ -0,0 +1,76 @@
+--TEST--
+Foreach loop tests - using an array element as the $value
+--FILE--
+<?php
+
+$a=array("a", "b", "c");
+$v=array();
+foreach($a as $v[0]) {
+    var_dump($v);
+}
+var_dump($a);
+var_dump($v);
+
+echo "\n";
+$a=array("a", "b", "c");
+$v=array();
+foreach($a as $k=>$v[0]) {
+    var_dump($k, $v);
+}
+var_dump($a);
+var_dump($k, $v);
+?>
+--EXPECT--
+array(1) {
+  [0]=>
+  string(1) "a"
+}
+array(1) {
+  [0]=>
+  string(1) "b"
+}
+array(1) {
+  [0]=>
+  string(1) "c"
+}
+array(3) {
+  [0]=>
+  string(1) "a"
+  [1]=>
+  string(1) "b"
+  [2]=>
+  string(1) "c"
+}
+array(1) {
+  [0]=>
+  string(1) "c"
+}
+
+int(0)
+array(1) {
+  [0]=>
+  string(1) "a"
+}
+int(1)
+array(1) {
+  [0]=>
+  string(1) "b"
+}
+int(2)
+array(1) {
+  [0]=>
+  string(1) "c"
+}
+array(3) {
+  [0]=>
+  string(1) "a"
+  [1]=>
+  string(1) "b"
+  [2]=>
+  string(1) "c"
+}
+int(2)
+array(1) {
+  [0]=>
+  string(1) "c"
+}

tests/core/lang/func_get_arg-001.phpt

@@ -0,0 +1,18 @@
+--TEST--
+func_get_arg test (PHP7)
+--FILE--
+<?php
+
+function foo($a)
+{
+   $a=5;
+   echo func_get_arg(0);
+}
+
+function main() {
+    foo(2);
+    echo "\n";
+}
+?>
+--EXPECT--
+5

tests/core/lang/func_get_arg_variation.phpt

@@ -0,0 +1,29 @@
+--TEST--
+func_get_arg test
+--FILE--
+<?php
+
+function foo($a)
+{
+   $a=5;
+   try {
+       echo func_get_arg(-1);
+   } catch (\Error $e) {
+       echo $e->getMessage() . \PHP_EOL;
+   }
+
+   try {
+       echo func_get_arg(2);
+   } catch (\Error $e) {
+       echo $e->getMessage() . \PHP_EOL;
+   }
+}
+
+function main() {
+    foo(2);
+}
+
+?>
+--EXPECT--
+func_get_arg(): Argument #1 ($position) must be greater than or equal to 0
+func_get_arg(): Argument #1 ($position) must be less than the number of the arguments passed to the currently executed function