3v4l.org

run code in 500+ PHP versions simultaneously
<?php $str = '11131221133112'; var_export( preg_replace( '/(\d)\1*\K(?!$)/', ' ', $str ) );
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.31, 8.3.0 - 8.3.32, 8.4.1 - 8.4.23, 8.5.0 - 8.5.8
'111 3 1 22 11 33 11 2'
preferences:
100.07 ms | 1276 KiB | 4 Q