3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = 9010201; var_export( preg_replace( '~.\K(?=.{2}+$)~', " ", $str ) );
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.13
'90102 01'

preferences:
135.7 ms | 406 KiB | 5 Q