3v4l.org

run code in 300+ PHP versions simultaneously
<?php namespace { echo __NAMESPACE__ . "\n"; } namespace Foo { echo __NAMESPACE__ . "\n"; }
Output for 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
Foo
preferences:
63.02 ms | 406 KiB | 5 Q