diff --git a/reference/array/functions/array-walk.xml b/reference/array/functions/array-walk.xml
index e1a15bdef9..fed4769414 100644
--- a/reference/array/functions/array-walk.xml
+++ b/reference/array/functions/array-walk.xml
@@ -53,6 +53,14 @@
original array itself.
+
+
+ Many internal functions (for example strtolower)
+ will throw a warning if more than the expected number of argument
+ are passed in and are not usable directly as
+ funcname.
+
+
Only the values of the array may potentially be
changed; its structure cannot be altered, i.e., the programmer cannot
diff --git a/reference/filesystem/functions/popen.xml b/reference/filesystem/functions/popen.xml
index c4f89faf47..0d58563f71 100644
--- a/reference/filesystem/functions/popen.xml
+++ b/reference/filesystem/functions/popen.xml
@@ -51,7 +51,10 @@
only be used for reading or writing) and must be closed with
pclose. This pointer may be used with
fgets, fgetss, and
- fwrite.
+ fwrite. When the mode is 'r', the returned
+ file pointer equals to the STDOUT of the command, when the mode
+ is 'w', the returned file pointer equals to the STDIN of the
+ command.
If an error occurs, returns &false;.