php 数组中未定义的索引，当索引实际上存在时

Question

Ok so I know what an undefined index means but I SWEAR i have this index in my array. Lets have some context:

I have an array of objects in javascript, each object looks like so:

let obj = {
          crop: arr['Crop'],
          pests: arr['Pests'],
          chemical, 
          product: arr['Product'],
          footnote: arr['Footnote'],
          rate: arr['Rate / ha'],
          max_no: arr['Max No'],
          hi: arr['HI'],
          mrl,
          pcs_no: arr['PCS No'],
          supplier: arr['Supplier'],
          useByDate: arr['Use By Date'],
          footnote: arr['Footnote'],
          comment: arr['Comment']
        };

I then use JSON.stringify() and send the array to a php handler, simple enough, yes. I then use json_decode($array, true) and use a foreach loop on said array. The only 2 indexes that are "undefined" are supplier and pests. Right now I have ignored all the logic and just echo back each element in the foreach loop and I can see the indexes in the response. So I am very confused. If I uncomment the logic then I get the undefined error again.

Here is the php code:

$results = array();

      $pests = json_decode($_POST['stringedArray'], true);
      
      foreach($pests as $pest) {
        $newCode = randomString(16);

        $chemCodes = array();
        $mrlCodes = array();

        $chems = $pest['chemical'];
        $mrls = $pest['mrl'];

        if(is_array($chems)) {
          foreach($chems as $chem) {
            if(!empty($chem)) {
              $code = processChemical($connection, trim($chem));
              array_push($chemCodes, $code);
            }
          }
        } else {
          $code = processChemical($connection, trim($chems));
          array_push($chemCodes, $code);
        }

        if(is_array($mrls)) {
          foreach($mrls as $mrl) {
            if(!empty($mrl)) {
              $code = processMrl($connection, trim($mrl));
              array_push($mrlCodes, $code);
            }
          }
        } else {
          $code = processMrl($connection, trim($mrls));
          array_push($mrlCodes, $code);
        }

        $cropCode = processCrop($connection, trim($pest['crop']));
        $pestCode = processPest($connection, trim($pest['pests'])); //UNDEFINED INDEX 'pests'

        $supplierCode = processCompany($connection, trim($pest['supplier'])); //UNDEFINED INDEX 'supplier'

        $data = array(
          "code" => $newCode,
          "crop_code" => $cropCode,
          "pests" => $pestCode,
          "product" => (!empty($pest['product']) ? $pest['product'] : NULL),
          "footnote" => (!empty($pest['footnote']) ? $pest['footnote'] : NULL),
          "rate" => (!empty($pest['rate']) ? $pest['rate'] : NULL),
          "max_no" => (!empty($pest['max_no']) ? $pest['max_no'] : NULL),
          "hi" => (!empty($pest['hi']) ? $pest['hi'] : NULL),
          "pcs_no" => (!empty($pest['pcs_no']) ? $pest['pcs_no'] : NULL),
          "supplier_code" => $supplierCode,
          "use_by_date" => (!empty($pest['useByDate']) ? $pest['useByDate'] : NULL),
          "comment" => (!empty($pest['comment']) ? $pest['comment'] : NULL),
          "status" => 'active'
        );

        $check = checkForPest($connection, $data);

        foreach($chemCodes as $chemCode) {
          addPestChemical($connection, $chemCode, $newCode);
        }

        foreach($mrlCodes as $mrlCode) {
          addPestMrl($connection, $mrlCode, $newCode);
        }

        //$result = addPest($connection, $data);

        array_push($results, $pest);
         
      }

      echo json_encode($results);

Answer 1

I fixed it by adding || null|| null to the end of each value in the object before it was stringified. I guess if there is no value it just acts like the index doesn't exist.