diff --git a/reference/sem/functions/sem-get.xml b/reference/sem/functions/sem-get.xml
index c6888153ae..3745aee112 100644
--- a/reference/sem/functions/sem-get.xml
+++ b/reference/sem/functions/sem-get.xml
@@ -101,6 +101,19 @@
+
+ &reftitle.notes;
+
+
+ When using sem_get to access a semaphore created
+ outside PHP, note that the semaphore must have been created as a set of 3
+ semaphores (for example, by specifying 3 as the nsems
+ parameter when calling the C semget() function),
+ otherwise PHP will be unable to access the semaphore.
+
+
+
+
&reftitle.seealso;