From 402fca265344c86e63fac657bc6a51d50f22a9a7 Mon Sep 17 00:00:00 2001
From: Andrey Andreev <narf@devilix.net>
Date: Tue, 7 Mar 2017 19:02:34 +0200
Subject: [PATCH] Add optional allow_objects param to is_string()

When set to true, will allow objects implementing __toString() to pass is_string() validation
---
 ext/standard/basic_functions.c                |  3 +-
 .../tests/general_functions/is_string.phpt    | 39 +++++++++++++++++--
 ext/standard/type.c                           | 22 ++++++++++-
 3 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/ext/standard/basic_functions.c b/ext/standard/basic_functions.c
index 2079afa38a3fe..17b2cde9780d4 100644
--- a/ext/standard/basic_functions.c
+++ b/ext/standard/basic_functions.c
@@ -2547,8 +2547,9 @@ ZEND_BEGIN_ARG_INFO(arginfo_is_float, 0)
 	ZEND_ARG_INFO(0, var)
 ZEND_END_ARG_INFO()
 
-ZEND_BEGIN_ARG_INFO(arginfo_is_string, 0)
+ZEND_BEGIN_ARG_INFO_EX(arginfo_is_string, 0, 0, 1)
 	ZEND_ARG_INFO(0, var)
+	ZEND_ARG_INFO(0, allow_objects)
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_INFO(arginfo_is_array, 0)
diff --git a/ext/standard/tests/general_functions/is_string.phpt b/ext/standard/tests/general_functions/is_string.phpt
index b8c82b187bd71..c3c7dcf659ecd 100644
--- a/ext/standard/tests/general_functions/is_string.phpt
+++ b/ext/standard/tests/general_functions/is_string.phpt
@@ -140,12 +140,31 @@ foreach ($not_strings as $type ) {
   var_dump( is_string($type) );
 }
 
+echo "\n*** Testing is_string() second parameter ***\n";
+
+echo "-- objects not allowed; string input --\n";
+var_dump(is_string("string", false));
+echo "-- objects allowed; string input --\n";
+var_dump(is_string("string", true));
+
+echo "-- objects not allowed; non-__toString() object input --\n";
+var_dump(is_string(new stdClass(), false));
+echo "-- objects allowed; non-__toString() object input --\n";
+var_dump(is_string(new stdClass(), true));
+
+$toStringObject = new class() { public function __toString() { return ''; } };
+echo "-- objects not allowed; __toString() object input --\n";
+var_dump(is_string($toStringObject, false));
+echo "-- objects allowed; __toString() object input --\n";
+var_dump(is_string($toStringObject, true));
+
+
 echo "\n*** Testing error conditions ***\n";
 //Zero argument
 var_dump( is_string() );
 
 //arguments more than expected 
-var_dump( is_string("string", "test") );
+var_dump( is_string("string", false, "test") );
  
 echo "Done\n";
 
@@ -293,11 +312,25 @@ bool(false)
 -- Iteration 45 --
 bool(false)
 
+*** Testing is_string() second parameter ***
+-- objects not allowed; string input --
+bool(true)
+-- objects allowed; string input --
+bool(true)
+-- objects not allowed; non-__toString() object input --
+bool(false)
+-- objects allowed; non-__toString() object input --
+bool(false)
+-- objects not allowed; __toString() object input --
+bool(false)
+-- objects allowed; __toString() object input --
+bool(true)
+
 *** Testing error conditions ***
 
-Warning: is_string() expects exactly 1 parameter, 0 given in %s on line %d
+Warning: is_string() expects at least 1 parameter, 0 given in %s on line %d
 bool(false)
 
-Warning: is_string() expects exactly 1 parameter, 2 given in %s on line %d
+Warning: is_string() expects at most 2 parameters, 3 given in %s on line %d
 bool(false)
 Done
diff --git a/ext/standard/type.c b/ext/standard/type.c
index a8000504628f2..5b1c0b5f4ad66 100644
--- a/ext/standard/type.c
+++ b/ext/standard/type.c
@@ -301,12 +301,30 @@ PHP_FUNCTION(is_float)
 }
 /* }}} */
 
-/* {{{ proto bool is_string(mixed var)
+/* {{{ proto bool is_string(mixed var [, bool allow_objects])
    Returns true if variable is a string
    Warning: This function is special-cased by zend_compile.c and so is usually bypassed */
 PHP_FUNCTION(is_string)
 {
-	php_is_type(INTERNAL_FUNCTION_PARAM_PASSTHRU, IS_STRING);
+	zval *var;
+	zend_bool allow_objects = 0;
+
+	ZEND_PARSE_PARAMETERS_START(1, 2)
+		Z_PARAM_ZVAL(var)
+		Z_PARAM_OPTIONAL Z_PARAM_BOOL(allow_objects)
+	ZEND_PARSE_PARAMETERS_END_EX(RETURN_FALSE);
+
+	switch (Z_TYPE_P(var)) {
+		case IS_STRING:
+			RETURN_TRUE;
+			break;
+		case IS_OBJECT:
+			RETURN_BOOL(allow_objects == 1 && Z_OBJCE_P(var)->__tostring);
+			break;
+		default:
+			RETURN_FALSE;
+			break;
+	}
 }
 /* }}} */