diff --git a/standards/php.md b/standards/php.md
index 7cf4a0c..e8a9602 100644
--- a/standards/php.md
+++ b/standards/php.md
@@ -54,6 +54,14 @@ Use `elseif` where possible instead of `else if`.
 
 Namespaces must be surrounded with new line elements.
 
+## Class Constants
+
+Class constants MUST have a access modifier
+
+```php
+public CONST_NAME = ...;
+```
+
 ## Deprecated functions and variables
 
 The following functions and (super-) global variables MUST NOT be used.