Why AJAX POST results in an Undefined array key error?-CodePudding

I am trying to pass a text string to a PHP Variable using AJAX, but I keep getting this error when POST fires:

Warning: Undefined array key "mydata"

the alert fires and displays the value correctly, but then the PHP page displays the mentioned error. What's wrong here?

AJAX:

$("#display_tasks").click(function() {
    var name = $(this).text();
    var namecut = name.substr(0,name.indexOf(' |'));
    $.ajax({
         type: 'POST',
         url: 'opentask.php',
         data: {mydata : namecut},
         success:function(data) {
             alert(data);
         }
    });
});

PHP:

$taskname = $_POST['mydata'];
echo $taskname;

CodePudding user response：

Please remove href="opentask.php" from the following line (you just need the ajax to call opentask.php) :

<a id="display_tasks" href="opentask.php">

Secondly , please use isset to check the existence of $_POST['mydata'] before assigning it to $taskname

So please use

<script
  src="https://code.jquery.com/jquery-3.6.1.js"
  integrity="sha256-3zlB5s2uwoUzrXK3BT7AX3FyvojsraNFxCc2vC/7pNI="
  crossorigin="anonymous"></script>

<?php 
$displaytaskrowresult="ABCD | Text";
echo '<a id="display_tasks">'.$displaytaskrowresult.'</a>'; ?> 

<script>
$("#display_tasks").click(function() {
    var name = $(this).text();
    var namecut = name.substr(0,name.indexOf(' |'));
    $.ajax({
         type: 'POST',
         url: 'opentask.php',
         data: {mydata : namecut},
         success:function(data) {
             alert(data);
             window.location.href="opentask.php";
         }
    });
});

</script>

and

opentask.php

<?php
ini_set('display_errors', 1); ini_set('display_startup_errors', 1); error_reporting(E_ALL);

$taskname = isset($_POST['mydata']) ? $_POST['mydata']: '' ;
echo $taskname;
?>

Please visit the following sandbox to see the effect:

http://www.createchhk.com/SOanswers/subj/test1.php

[Additional point]

If you just want to test POST request to be displayed in the target page, please use a form submission. (because ajax will only return the result back to the calling page in the success block.)

CodePudding user response：

You are using $_POST['mydata'] always, not just when receiving AJAX request. And when you are just showing the page, the superglobal array $_POST haven't got an element indexed by 'mydata'. That's why you get the error.

A way to avoid this is to separate AJAX receiving request to another file. This is like is done by several PHP applications.

A simpler way you can use to test is to check $_POST, for example you can do this:

if (!empty($_POST)) {
    $taskname = $_POST['mydata'];
    echo $taskname;
}

That way you only try to use $_POST['mydata]` when you are receiving a POST. Also, if element 'mydata' is not present, you will still get an undefined array key error.

CodePudding user response：

Replace var name = $(this).text();

with var name= $(this).attr('value'); or document.getElementById('name').value

name is the text input name I think this will work and test if it gets by console.log(name) first