Online PHP editor | refs for qQNTv

<?php function flat_map(callable $callback, array $collection) { return array_merge([], ...array_map($callback, $collection)); }; var_dump( array_map(function ($el) { return str_split($el); }, ["two birds", "three green peas"]) ); var_dump( flat_map(function ($el) { return str_split($el); }, ["two birds", "three green peas"]) ); var_dump( flat_map(function ($el) { return str_split($el); }, []) );