Add property and method modifier order chapter

wordpress-coding-standards/php.md

@@ -660,6 +660,32 @@ _Usage in WordPress Core_
 
 Visibility for class constants can not be used in WordPress Core until the minimum PHP version has been raised to PHP 7.1.
 
+### Property and method modifier order
+
+When using multiple modifiers for a property or method declaration, the order should be as follows:
+
+1. First the optional `abstract` or `final` keyword.
+2. Next a visibility keyword.
+3. Lastly, the optional `static` keyword.
+
+```php
+// Correct.
+abstract class Foo {
+    public static $foo;
+
+    abstract protected static function bar();
+}
+
+// Incorrect.
+abstract class Foo {
+    static public $foo;
+
+    static protected final function bar() {
+        // Code.
+    };
+}
+```
+
 ## Control Structures
 
 ### Use `elseif`, not `else if`