php级联

$(document).ready(function(){     $("select#category").change(function(){         // Post string         var post_string = "type=" + $(this).val();          // Send the request and update sub category dropdown         $.ajax({             type: "POST",             data: post_string,             dataType: "json",             cache: false,             url: 'json.php',             timeout: 2000,             error: function() {                 alert("Failed to submit");             },             success: function(data) {                  // Clear all options from sub category select                 $("select#sub_category option").remove();                  // Fill sub category select                 $.each(data, function(i, j){                     var row = "<option value=\"" + j.value + "\">" + j.text + "</option>";                     $(row).appendTo("select#sub_category");                 });             }         });     });     });

<select name="category" id="category">     <option value="">-- Select Value --</option>     <option value="1">Dog</option>     <option value="2">Cat</option> </select>  <select name="sub_category" id="sub_category">     <option value="">-- Select First Value --</option> </select>

$json = array();  if ($_POST['type'] == 1) {     $json[] = array(         'value' => '1',         'text' => 'Staffordshire Bull Terrier'     );     $json[] = array(         'value' => '2',         'text' => 'Labrador Retriever/American Pit Bull Mix'     );     $json[] = array(         'value' => '3',         'text' => 'German Short Hair Pointer'     ); } elseif ($_POST['type'] == 2) {     $json[] = array(         'value' => '4',         'text' => 'Domestic Medium Hair'     ); }  echo json_encode($json);