3v4l.org

run code in 500+ PHP versions simultaneously
<?php // Why is this allowed ? class MyDateTimeImmutable extends DateTimeImmutable implements DateTimeInterface { public function format(string $format): string { return 'Why is this allowed?'; } } // And why is this disallowed ? // Fatal error: DateTimeInterface can't be implemented by user classes class MyTime implements DateTimeInterface { }

Here you find the average performance (time & memory) of each version. A grayed out version indicates it didn't complete successfully (based on exit-code).

VersionSystem time (s)User time (s)Memory (MiB)
8.5.90.0100.00716.87

preferences:
44.11 ms | 480 KiB | 5 Q