Online PHP editor | output for OSfKR

Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45: Fatal error: Class 'DateTimeImmutable' not found in /in/OSfKR on line 4
Process exited with code 255.
Output for 5.5.17 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.34, 8.3.0 - 8.3.35, 8.4.1 - 8.4.26, 8.5.0 - 8.5.11: bool(false) object(DateTimeImmutable)#1 (3) { ["date"]=> string(26) "2019-10-10 15:32:38.000000" ["timezone_type"]=> int(2) ["timezone"]=> string(1) "Z" }
Output for 5.5.14 - 5.5.16: bool(false) object(DateTimeImmutable)#2 (3) { ["date"]=> string(26) "2019-10-10 15:32:38.000000" ["timezone_type"]=> int(2) ["timezone"]=> string(1) "Z" }
Output for 5.5.4 - 5.5.13: bool(false) object(DateTimeImmutable)#2 (3) { ["date"]=> string(19) "2019-10-10 15:32:38" ["timezone_type"]=> int(2) ["timezone"]=> string(1) "Z" }
Output for 5.5.0 - 5.5.3: bool(false) object(DateTime)#2 (3) { ["date"]=> string(19) "2019-10-10 15:32:38" ["timezone_type"]=> int(2) ["timezone"]=> string(1) "Z" }
Output for 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17: Warning: Unexpected character in input: '\' (ASCII=92) state=1 in /in/OSfKR on line 4 Warning: Unexpected character in input: '\' (ASCII=92) state=1 in /in/OSfKR on line 9 Fatal error: Class 'DateTimeImmutable' not found in /in/OSfKR on line 4
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.2 - 4.3.11, 4.4.0 - 4.4.9: Warning: Unexpected character in input: '\' (ASCII=92) state=1 in /in/OSfKR on line 4 Warning: Unexpected character in input: '\' (ASCII=92) state=1 in /in/OSfKR on line 9 Fatal error: Undefined class name 'datetimeimmutable' in /in/OSfKR on line 4