3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = 'a\\\\,b,c\\,d'; $str2 = 'a\\\\,b,c\\,d'; print_r(preg_split('/(?<!(?<!\\\\)\\\\),/', $str)); print_r(preg_split('/(?<![^\\\\])(?<!\\\\),/', $str2));

preferences:
37.18 ms | 402 KiB | 5 Q