printing zero in case of null in foreach loop

A php code is shown here

foreach ($icx_json_date as $key_date => $icx_value_date) {

        echo $icx_value_date["isd_out_traffic"] . ", ";
    }

the output for this code is

, , , , , , 14449.25, 881.50,

I want to replace the null output with zero and show the output as

0, 0, 0, 0, 0, 0, 14449.25, 881.50,

what changes should be done to do so?