Fix #81475: stream_isatty emits warning with attached stream wrapper

We must not issue warnings, if `show_err` is false.

Closes GH-7513.

Author: cmb69

NEWS

@@ -24,6 +24,10 @@ PHP                                                                        NEWS
   . Fixed bug #80663 (Recursive SplFixedArray::setSize() may cause double-free).
     (cmb, Nikita, Tyson Andre)
 
+- Streams:
+  . Fixed bug #81475 (stream_isatty emits warning with attached stream wrapper).
+    (cmb)
+
 - XML:
   . Fixed bug #70962 (XML_OPTION_SKIP_WHITE strips embedded whitespace).
     (Aliaksandr Bystry, cmb)

ext/standard/tests/filters/bug81475.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Bug #81475 (stream_isatty emits warning with attached stream wrapper)
+--FILE--
+<?php
+$stdout = fopen('php://stdout', 'wb');
+stream_filter_append($stdout, 'string.toupper');
+var_dump(stream_isatty($stdout));
+?>
+--EXPECT--
+bool(false)

main/streams/cast.c

@@ -295,7 +295,9 @@ PHPAPI int _php_stream_cast(php_stream *stream, int castas, void **ret, int show
 	}
 
 	if (php_stream_is_filtered(stream)) {
-		php_error_docref(NULL, E_WARNING, "cannot cast a filtered stream on this system");
+		if (show_err) {
+			php_error_docref(NULL, E_WARNING, "cannot cast a filtered stream on this system");
+		}
 		return FAILURE;
 	} else if (stream->ops->cast && stream->ops->cast(stream, castas, ret) == SUCCESS) {
 		goto exit_success;