3v4l.org

run code in 300+ PHP versions simultaneously
<?php $string = ',1,2,,4,5,,,,6,,,,'; echo preg_replace('/,\K,+/', '', trim($string, ','));
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
1,2,4,5,6

preferences:
90.97 ms | 1240 KiB | 4 Q