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<?php $str = 'a\\\\,b,c\\,d'; var_dump(preg_split('/(?<!(?<!\\\\)\\\\),/', $str)); preg_match_all('/[^\\\\]\\\\,|([^,]+?)/', $str, $matches); print_r(array_filter($matches[1]));

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32.2 ms | 402 KiB | 5 Q