This is apparently fixed

tests/output/ob_start_basic_unerasable_005.phpt

@@ -1,7 +1,5 @@
 --TEST--
 ob_start(): Ensure unerasable buffer cannot be flushed by ob_flush().
---XFAIL--
-On PHP5, ob_flush() DOES clear the buffer. See bug: 46897
 --FILE--
 <?php
 function callback($string) {
@@ -19,9 +17,9 @@ var_dump(ob_get_contents());
 ?>
 --EXPECTF--
 [callback:1]Attempt to flush unerasable buffer - should fail... 
-Notice: ob_flush(): failed to flush buffer callback in %s on line 11
+Notice: ob_flush(): failed to flush buffer callback. in %s on line 11
 bool(false)
 string(%d) "Attempt to flush unerasable buffer - should fail... 
-Notice: ob_flush(): failed to flush buffer callback in %s on line 11
+Notice: ob_flush(): failed to flush buffer callback. in %s on line 11
 bool(false)
-"
+"