Make encapsed strings fully dereferencable

This allows operations that were previously allowed on constant
strings on interpolated strings as well.

Author: nikic

Zend/tests/varSyntax/encapsed_string_deref.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Dereferencing operations on an encapsed string
+--FILE--
+<?php
+
+$bar = "bar";
+var_dump("foo$bar"[0]);
+var_dump("foo$bar"->prop);
+try {
+    var_dump("foo$bar"->method());
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+class FooBar { public static $prop = 42; }
+var_dump("foo$bar"::$prop);
+
+function foobar() { return 42; }
+var_dump("foo$bar"());
+
+?>
+--EXPECTF--
+string(1) "f"
+
+Warning: Trying to get property 'prop' of non-object in %s on line %d
+NULL
+Call to a member function method() on string
+int(42)
+int(42)

Zend/zend_language_parser.y

@@ -1102,6 +1102,7 @@ dereferencable_scalar:
 		T_ARRAY '(' array_pair_list ')'	{ $$ = $3; $$->attr = ZEND_ARRAY_SYNTAX_LONG; }
 	|	'[' array_pair_list ']'			{ $$ = $2; $$->attr = ZEND_ARRAY_SYNTAX_SHORT; }
 	|	T_CONSTANT_ENCAPSED_STRING		{ $$ = $1; }
+	|	'"' encaps_list '"'			 	{ $$ = $2; }
 ;
 
 scalar:
@@ -1118,7 +1119,6 @@ scalar:
 	|	T_START_HEREDOC T_ENCAPSED_AND_WHITESPACE T_END_HEREDOC { $$ = $2; }
 	|	T_START_HEREDOC T_END_HEREDOC
 			{ $$ = zend_ast_create_zval_from_str(ZSTR_EMPTY_ALLOC()); }
-	|	'"' encaps_list '"' 	{ $$ = $2; }
 	|	T_START_HEREDOC encaps_list T_END_HEREDOC { $$ = $2; }
 	|	dereferencable_scalar	{ $$ = $1; }
 	|	constant			{ $$ = $1; }