如何在AJAX成功函数中获取json数据

Question

This is my AJAX code to fetch dropdown record.

function item_value() {
  $.ajax({
    type: "POST",
    url: "ajax.php",
    contentType: "application/json; charset=utf-8",
    async: false,
    data: data,
    dataType: "json",
    success: function (json) {
      if (json == '') {
        alert('No Records');
      } else {
        alert(json);
        $.each(json, function (index, elem) {
          $("#item_select1").append("<option value=\"" + elem.value+ "\">" + elem.name+ "</option>");
        });
      }
    }
  });
}

This file is used to pull record or get get records in AJAX success.

Ajax.php

<?php
include('../dbconnection/comp_connect.php');
$qry_item="SELECT item_id,item_name,item_unit,rate,description,tax_id,status FROM item";
$view_item=$conn->prepare($qry_item);
$view_item->execute();
$rs_item=$view_item->fetch((PDO::FETCH_ASSOC))
$data = array('item_name' =>$rs_item['item_name'],
              'item_unit'=>$rs_item['item_unit'],
              'rate'=>$rs_item['rate'],
              'description'=>$rs_item['description'],
              'tax_id'=>$rs_item['tax_id']
             );
echo json_encode($data);
?>

Answer 1

It looks like the data that you're creating in PHP doesn't line up with what you're trying to do in your AJAX success function. The PHP code fetches one row from your database, so the JSON it will return will look like:

{
    "item_name": "something",
    "item_unit": "something",
    "rate": "something",
    "description": "something",
    "tax_id": "something"
}

But this part of your success function

$.each(json, function (index, elem) {
  $("#item_select1").append("<option value=\"" + elem.value + "\">" + elem.name + "</option>");
});

needs an collection of objects ( elem ) with name and value properties. Instead, with what you're getting from PHP, each elem will be a string or number, so elem.value and elem.name will be undefined.

Since you're using this to append options to a select, your PHP needs to return multiple rows, and the keys you assign in PHP need to match the properties you refer to in your success function. Something like this should be closer to what you want.

<?php
include('../dbconnection/comp_connect.php');
$qry_item = "SELECT item_id, item_name FROM item";
$view_item = $conn->prepare($qry_item);
$view_item->execute();
while ($item = $view_item->fetch((PDO::FETCH_ASSOC)) {
    $data[] = ['value' => $rs_item['item_id'], 'name' => $rs_item['item_name']];
}
echo json_encode($data);

Answer 2

In you php script make sure to add following headers before you print our the encoded data

header('Content-type: application/json');
echo json_encode($data);