fix bug #61272 ob_start callback get passed empty string

main/output.c

@@ -297,7 +297,6 @@ PHPAPI int php_output_clean(TSRMLS_D)
 	php_output_context context;
 
 	if (OG(active) && (OG(active)->flags & PHP_OUTPUT_HANDLER_CLEANABLE)) {
-		OG(active)->buffer.used = 0;
 		php_output_context_init(&context, PHP_OUTPUT_HANDLER_CLEAN TSRMLS_CC);
 		php_output_handler_op(OG(active), &context);
 		php_output_context_dtor(&context);
@@ -1226,7 +1225,6 @@ static inline int php_output_stack_pop(int flags TSRMLS_DC)
 			/* signal that we're cleaning up */
 			if (flags & PHP_OUTPUT_POP_DISCARD) {
 				context.op |= PHP_OUTPUT_HANDLER_CLEAN;
-				orphan->buffer.used = 0;
 			}
 			php_output_handler_op(orphan, &context);
 		}

tests/output/ob_017.phpt

@@ -27,8 +27,8 @@ Array
     [0] => 1: yes
     [1] => 4: !
 
-    [2] => 2: 
+    [2] => 2: no
     [3] => 0: yes!
 
-    [4] => 10: 
+    [4] => 10: no
 )