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<?php $array = [1,2,3,[5,6,7]]; $nu_array = null; $callback = function ( $item ) use(&$callback, &$nu_array) { if (!is_array($item)) { $nu_array[] = $item; } else if ( is_array( $item ) ) { foreach( array_values($item) as $v) { if ( !(is_array($v))) { $nu_array[] = $v; } else { $callback( $v ); continue; } } } }; array_walk($array, $callback); print_r($nu_array); $nu_array = []; array_walk_recursive($array, function ( $item ) use(&$nu_array ) { $nu_array[] = $item; } ); print_r($nu_array);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.27, 8.0.0 - 8.0.15, 8.1.0 - 8.1.2
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 5 [4] => 6 [5] => 7 ) Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 5 [4] => 6 [5] => 7 )

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