foreach ($table->find('tr') as $row) {
    $zero = $row->find('td',0)->innertext;
    $one = $row->find('td',1)->innertext;
    $two = $row->find('td',2)->innertext;
    $three = $row->find('td', 3)->innertext;
$json[] = [ 'zero' => $zero, 'one' => $one, 'two' => $two, 'three' => $three ];
}
echo json_encode($json,JSON_PRETTY_PRINT);

{
   "zero": "four",
   "one": "",
   "two": "",
   "three": ""
 },
 {
   "zero": "zero",
   "one": "one",
   "two": "two",
   "three": "three"
 },
 {
   "zero": "zero",
   "one": "one",
   "two": "two",
   "three": "three"
 },

{
   "zero": "zero",
   "one": "one",
   "two": "two",
   "three": "three",
   "four": "four"
},