Question 35965 in Jquery Question posted in
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Why AJAX POST results in an Undefined array key error? – Jquery

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;
Tags:

3

Answers


  1. 0

    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.

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  2. 0

    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

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  3. 0

    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.)

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