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<?php class A { } class B extends A { public self $instOfSelf; public parent $instOfParent; } $b = new B(); $b->instOfParent = new B(); # Allowed var_dump($b); $b->instOfParent = new A(); # Also allowed var_dump($b); $b->instOfSelf = new B(); # Allowed var_dump($b); $b->instOfSelf = new A(); # ERROR var_dump($b);
Output for 8.5.0 - 8.5.3
object(B)#1 (1) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> uninitialized(A) } } object(B)#1 (1) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> object(A)#3 (0) { } } object(B)#1 (2) { ["instOfSelf"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> uninitialized(A) } ["instOfParent"]=> object(A)#3 (0) { } } Fatal error: Uncaught TypeError: Cannot assign A to property B::$instOfSelf of type B in /in/n820F:21 Stack trace: #0 {main} thrown in /in/n820F on line 21
Process exited with code 255.
Output for 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18
object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> uninitialized(parent) } } object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(A)#3 (0) { } } object(B)#1 (2) { ["instOfSelf"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> uninitialized(parent) } ["instOfParent"]=> object(A)#3 (0) { } } Fatal error: Uncaught TypeError: Cannot assign A to property B::$instOfSelf of type self in /in/n820F:21 Stack trace: #0 {main} thrown in /in/n820F on line 21
Process exited with code 255.
Output for 8.0.0 - 8.0.30
object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> uninitialized(A) } } object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(A)#3 (0) { } } object(B)#1 (2) { ["instOfSelf"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> uninitialized(A) } ["instOfParent"]=> object(A)#3 (0) { } } Fatal error: Uncaught TypeError: Cannot assign A to property B::$instOfSelf of type B in /in/n820F:21 Stack trace: #0 {main} thrown in /in/n820F on line 21
Process exited with code 255.
Output for 7.4.0 - 7.4.33
object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> uninitialized(A) } } object(B)#1 (1) { ["instOfSelf"]=> uninitialized(self) ["instOfParent"]=> object(A)#3 (0) { } } object(B)#1 (2) { ["instOfSelf"]=> object(B)#2 (0) { ["instOfSelf"]=> uninitialized(B) ["instOfParent"]=> uninitialized(A) } ["instOfParent"]=> object(A)#3 (0) { } } Fatal error: Uncaught TypeError: Typed property B::$instOfSelf must be an instance of B, A used in /in/n820F:21 Stack trace: #0 {main} thrown in /in/n820F on line 21
Process exited with code 255.
Output for 7.2.0 - 7.2.33, 7.3.0 - 7.3.33
Parse error: syntax error, unexpected 'self' (T_STRING), expecting function (T_FUNCTION) or const (T_CONST) in /in/n820F on line 6
Process exited with code 255.

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