jquery ajax帖子不起作用

Question

I read many posts on this issue but I can not solve the problem. It seems that ajax() works fine, but the .php file fails to update the SQL database and returns no results to the ajax() function.

This is my code:

    var datastring=JSON.stringify(utnew)

    $.ajax({    
            type: "POST",
            url: "myulr-php",       
            data: datastring,
            dataType: "json",
            success: function(resto){
                       if (resto=="success"){
                         $("#pop-confermadatiuser").html("OK"); 
                       }else{ 
                         $("#pop-confermadatiuser").html("KO");
                       };
                    }

    });

The php code work, i have try. this is the code:

    header("Access-Control-Allow-Origin: *");
    $con = mysqli_connect("sql","xxx","xxx","xxx") or die ("could not connect database");

     $ck=1 ;
     if(isset($_POST['id']))
     {
        $id=$_POST['id'];
        $nome=$_POST['nome'];
        $cognome=$_POST['cognome'];
        $matricola=$_POST['matricola'];
        $mail=$_POST['mail'];
        $password=$_POST['password'];
        $ck=2
        $qry="UPDATE user SET nome='".$nome."', cognome='".$cognome."', mail='".$mail."', password='".$password."' where id=".$id." and matricola=".$matricola;

     $q=mysqli_query($con,$qry);
     if($q) {
             echo "success";
     } else {
             echo "error";
     };
      mysqli_close($con);
     };

     if(ck==1){
               echo "error2";
     };

Answer 1

The jQuery code is sending the POST data as a JSON string, but your PHP code is looking for standard key-value pairs.

You can change the Ajax call to send in key-value format. I can't see what utnew refers to in your code, usually that would be a Javascript object or the result of serializing an HTML form with $.serialize():

$.post("myurl.php", utnew, "json")
  .always(function(response) { console.log(response); }

Or you can change the PHP side to expect a JSON-encoded string in the POST payload rather than encoded key-value pairs:

<?php
    ...
    $data = json_decode(file_get_contents('php://input'));
    if (isset($data['id'])) { ... }

Whichever you choose, the problem you're having is the Ajax call sending a JSON-encoded string as the POST payload, but PHP expecting key-value pairs in $_POST.

The "json" data type argument to jQuery $.ajax or the shortcut method $.post tells jQuery what format to expect the return value in, so your PHP code should return a JSON-encoded string. Your PHP code is sending back a plain string, so you should either tell jQuery to expect that:

$.post(url, data, "text")

or have PHP send back a proper JSON-encode object:

echo json_encode(["result" => "success"]);

If you have PHP error logging on (you should) to a file you can debug your API endpoint with error_log, i.e. error_log(print_r($_POST,1)); would have given you some clues.