PHP Code (modified from Replacing empty string with nulls in array php):
$array = array(
'first' => NULL,
'second' => NULL
);
echo json_encode($array);
$array2 = array_map(function($value) {
return $value === NULL ? "" : $value;
}, $array); // array_map should walk through $array
echo json_encode($array2);
Output:
{"first":null,"second":null}
{"first":"","second":""}
1
solved put blank value instead of null in array value php [duplicate]