How to convert a multidimensional array to one dimension

How to convert a multi-dimensional array into a one-dimensional multi-dimensional array to print the results:
Array ([10] => prepare to buy [11] => do not prepare to change [12] => Array ([0] => 3-car [1] => City SUB) [13] => 33333 [14] => Array ([0] => medium [1] => small-sized) [15] => Full risk)
If you want to convert it to a one-dimensional one, keep the original KEY unchanged, and merge multiple dimensions, you finally want
Array ([10] => prepare to buy [11] => not prepare to change [12] => 3-car, city SUB [13] => 33333 [14] => medium and small-sized [15] => Full Insurance)

After a long time, I am confused. Please take a look

Reply to discussion (solution)

$ A = Array (10 => 'buy now ', 11 =>' do not change ', 12 => Array (0 => 'sedan 3 ', 1 => 'City sub'), 13 => 33333, 14 => Array (0 => 'medium-sized ', 1 => 'clever type '), 15 => 'quanshen',); foreach ($ a as $ k => $ v) {if (is_array ($ v )) $ a [$ k] = join (',', $ v);} print_r ($ );

Array ([10] => prepare to buy [11] => not prepare to change [12] => 3-car, city SUB [13] => 33333 [14] => medium and small-sized [15] => Full Insurance)

Upstairs is a positive solution.

$ A = array (10 => 'buy now ', 11 =>' do not change ', 12 => Array (0 => 'sedan 3 ', 1 => 'City sub'), 13 => 33333, 14 => Array (0 => 'medium-sized ', 1 => 'clever type '), 15 => 'completely dangerous ',); $ B = array (); foreach ($ a as $ k => $ v) {$ B [$ k] = $ v; if (is_array ($ v) {$ B [$ k] = $ v [0]. ','. $ v [1] ;}} print_r ($ B );

Array ([10] => prepare to buy [11] => not prepare to change [12] => 3-car, city SUB [13] => 33333 [14] => medium and small-sized [15] => Full Insurance)