3v4l.org

run code in 300+ PHP versions simultaneously
<?php $letters = 'абвгдеёжзийклмнопрстуфхцчшщыэюяabcdefghijklmnopqrstuvwxyz'; if (function_exists('mb_str_split')) { // PHP7.4 and higher var_export(array_fill_keys(mb_str_split($letters), [])); } else { // below PHP7.4 var_export(array_fill_keys(preg_split('~~u', $letters, 0, PREG_SPLIT_NO_EMPTY), [])); }
based on SKSZK
Output for 7.1.25 - 7.1.30, 7.2.0 - 7.2.33, 7.3.0 - 7.3.23, 7.4.0 - 7.4.11, 8.0.0alpha1 - rc2
array ( 'а' => array ( ), 'б' => array ( ), 'в' => array ( ), 'г' => array ( ), 'д' => array ( ), 'е' => array ( ), 'ё' => array ( ), 'ж' => array ( ), 'з' => array ( ), 'и' => array ( ), 'й' => array ( ), 'к' => array ( ), 'л' => array ( ), 'м' => array ( ), 'н' => array ( ), 'о' => array ( ), 'п' => array ( ), 'р' => array ( ), 'с' => array ( ), 'т' => array ( ), 'у' => array ( ), 'ф' => array ( ), 'х' => array ( ), 'ц' => array ( ), 'ч' => array ( ), 'ш' => array ( ), 'щ' => array ( ), 'ы' => array ( ), 'э' => array ( ), 'ю' => array ( ), 'я' => array ( ), 'a' => array ( ), 'b' => array ( ), 'c' => array ( ), 'd' => array ( ), 'e' => array ( ), 'f' => array ( ), 'g' => array ( ), 'h' => array ( ), 'i' => array ( ), 'j' => array ( ), 'k' => array ( ), 'l' => array ( ), 'm' => array ( ), 'n' => array ( ), 'o' => array ( ), 'p' => array ( ), 'q' => array ( ), 'r' => array ( ), 's' => array ( ), 't' => array ( ), 'u' => array ( ), 'v' => array ( ), 'w' => array ( ), 'x' => array ( ), 'y' => array ( ), 'z' => array ( ), )