adding some tests for string offsets

tests/strings/offsets_chaining_1.phpt

@@ -0,0 +1,12 @@
+--TEST--
+testing the behavior of string offset chaining
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$string = "foobar";
+var_dump($string[0][0][0][0]);
+?>
+--EXPECTF--
+string(1) "f"
+

tests/strings/offsets_chaining_2.phpt

@@ -0,0 +1,12 @@
+--TEST--
+testing the behavior of string offset chaining
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$string = "foobar";
+var_dump($string{0}{0}[0][0]);
+?>
+--EXPECTF--
+string(1) "f"
+

tests/strings/offsets_chaining_3.phpt

@@ -0,0 +1,12 @@
+--TEST--
+testing the behavior of string offset chaining
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$string = "foobar";
+var_dump(isset($string[0][0][0][0]));
+?>
+--EXPECTF--
+bool(true)
+

tests/strings/offsets_chaining_4.phpt

@@ -0,0 +1,12 @@
+--TEST--
+testing the behavior of string offset chaining
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$string = "foobar";
+var_dump(isset($string{0}{0}[0][0]));
+?>
+--EXPECTF--
+bool(true)
+

tests/strings/offsets_chaining_5.phpt

@@ -0,0 +1,22 @@
+--TEST--
+testing the behavior of string offset chaining
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$array = array('expected_array' => "foobar");
+var_dump(isset($array['expected_array']));
+var_dump($array['expected_array']);
+var_dump(isset($array['expected_array']['foo']));
+var_dump($array['expected_array']['foo']);
+var_dump(isset($array['expected_array']['foo']['bar']));
+var_dump($array['expected_array']['foo']['bar']);
+?>
+--EXPECTF--
+bool(true)
+string(6) "foobar"
+bool(true)
+string(1) "f"
+bool(true)
+string(1) "f"
+

tests/strings/offsets_general.phpt

@@ -0,0 +1,34 @@
+--TEST--
+testing the behavior of string offsets
+--INI--
+error_reporting=E_ALL | E_DEPRECATED
+--FILE--
+<?php
+$string = "foobar";
+var_dump($string[0]);
+var_dump($string[1]);
+var_dump(isset($string[0]));
+var_dump(isset($string[0][0]));
+var_dump($string["foo"]);
+var_dump(isset($string["foo"]["bar"]));
+var_dump($string{0});
+var_dump($string{1});
+var_dump(isset($string{0}));
+var_dump(isset($string{0}{0}));
+var_dump($string{"foo"});
+var_dump(isset($string{"foo"}{"bar"}));
+?>
+--EXPECT--
+string(1) "f"
+string(1) "o"
+bool(true)
+bool(true)
+string(1) "f"
+bool(true)
+string(1) "f"
+string(1) "o"
+bool(true)
+bool(true)
+string(1) "f"
+bool(true)
+