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<?php $nu_array = null; $callback = function ( $item ) use(&$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; } } } }; $array = array( 'a',array(1,2), 'b',array(3,4, array(5,6, array('c', array(7,8)))) ); array_walk($array, $callback); print_r($nu_array); /** Array ( [0] => a [1] => 1 [2] => 2 [3] => b [4] => 3 [5] => 4 [6] => 5 [7] => 6 [8] => c [9] => 7 [10] => 8 ) **/
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Warning: Undefined variable $callback in /in/l26Xg on line 15 Fatal error: Uncaught Error: Value of type null is not callable in /in/l26Xg:15 Stack trace: #0 [internal function]: {closure}(Array, 3) #1 /in/l26Xg(24): array_walk(Array, Object(Closure)) #2 {main} thrown in /in/l26Xg on line 15
Process exited with code 255.
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.31, 7.4.0 - 7.4.33
Notice: Undefined variable: callback in /in/l26Xg on line 15 Fatal error: Uncaught Error: Function name must be a string in /in/l26Xg:15 Stack trace: #0 [internal function]: {closure}(Array, 3) #1 /in/l26Xg(24): array_walk(Array, Object(Closure)) #2 {main} thrown in /in/l26Xg on line 15
Process exited with code 255.
Output for 7.3.32 - 7.3.33
Fatal error: Uncaught Error: Function name must be a string in /in/l26Xg:15 Stack trace: #0 [internal function]: {closure}(Array, 3) #1 /in/l26Xg(24): array_walk(Array, Object(Closure)) #2 {main} thrown in /in/l26Xg on line 15
Process exited with code 255.
Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.28
Notice: Undefined variable: callback in /in/l26Xg on line 15 Fatal error: Function name must be a string in /in/l26Xg on line 15
Process exited with code 255.
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17
Parse error: syntax error, unexpected T_FUNCTION in /in/l26Xg on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected T_FUNCTION in /in/l26Xg on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/l26Xg on line 3
Process exited with code 255.

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