Explode（）函数将字符串分解为2个后续数组php

Question

I'm trying to split the $param variable below in the format

listofitems//listofitems//listofitems...

where each item is in the format

event,event,event,event...

into individual events (numbers) which are passed to my checkuseritems function. At the moment I'm only getting the first listofitems (1,4,9,7,5,8) and then 149758 with the echo functions. Why are the other two lists being ignored?

   $param= "1,4,9,7,5,8//5,8,9,6,4,2//8";
   $item = explode("//",$param);
   $allitemslength = count($item);
   $alluseritems["list"] = array();
for ($x = 0; $x < $allitemslength; $x++) {
    echo($item[$x]);


   $id = explode(",",$item[$x]);
   $arrlength = count($id);



    $response["item"] = array();


   for($x = 0; $x < $arrlength; $x++) {

 echo ($id[$x]);

  //  $result= $db->checkuseritems($id[$x]);
}
}