Add object instantiation chapter

wordpress-coding-standards/php.md

@@ -755,6 +755,23 @@ abstract class Foo {
 }
 ```
 
+### Object instantiation
+
+When instantiating a new object instance, parenthesis must always be used, even when not strictly necessary.
+There should be no space between the name of the class being instantiated and the opening parenthesis.
+Assigning the return value of an object instantiation by reference is not allowed (new by reference has not been supported by PHP for quite a long while now).
+
+```php
+// Correct.
+$foo = new Foo();
+$anonymous_class = new class() { ... };
+$instance = new static();
+
+// Incorrect.
+$foo = & new Foo;
+$foo = new Foo ();
+```
+
 ## Control Structures
 
 ### Use `elseif`, not `else if`