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I'm writing a simple delete function. This function deletes entries in a list that is being outputted by PHP. This is what happens:

  1. The javascript selects the checked boxes in this list and gets its ID 1,2,3etc.
  2. The created array is converted to JSON using JSON.stringify
  3. PHP gets the POST and decodes it using json_decode() (this fails)

$(document).ready(function(){

    $('.action_trash').on('click', function(){

        //Select items to trash
        var TrashItems = [];
        $('input:checked').each(function() {

            TrashItems.push($(this).attr("id"));
        });
        //Convert to JSON
        var TrashJSON = JSON.stringify(TrashItems);
        alert (TrashJSON);
        $.ajax({
            type: "POST",
            url: "pages/forms_intake/actions/trash/model_trash.php",
            data: {TrashItems:TrashItems}, 
            cache: false,

            success: function(){
                // do stuff to remove trashed elements from list.
            }
        }); 
    });     
});

I'm trying to convert the simple Javascript array to JSON. But I think the JSON is invalid. When I alert the TrashJSON variable, this is the output: ["31","32"]

<?php
session_start();
include "../../../../php/config.php";

$TrashJSON = $_POST['TrashItems'];
var_dump(json_decode($TrashJSON));

//Trash items
//$TrashQuery = mysqli_query ($mysqli, "UPDATE forms_intake SET item_trashed=1 WHERE formid='$TrashInt'"); 

//Close connection
mysqli_close($mysqli);
?>

When I run this, I'm getting this error:

<br />
<b>Warning</b>:  json_decode() expects parameter 1 to be string, array given in <b>/home/nickvmf103/domains/a-training.nl/public_html/sotwebapp/pages/forms_intake/actions/trash/model_trash.php</b> on line <b>7</b><br />
NULL

According to the PHP manual on json_decode, null gets outputted if the JSON is invalid.

So my question is: How to correctly format the JSON in my javascript? So that it can be passed to PHP and converted to a PHP array.

Additional info: When successfully converted to PHP array, I will use implode to put " OR " between the array values, convert it to a string and use it in my SQL query WHERE statement to trash the items that were checked on my page.

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1  
You don't need to use JSON when sending an array from jQuery to PHP. If you send the array, jQuery will URL-encode it properly, and PHP will automatically decode it. –  Barmar 2 days ago
    
Very true - I've expanded my answer slightly to include that option. –  Seidr 2 days ago

1 Answer 1

up vote 1 down vote

In order for the existing PHP to function how you expect, you need to send TrashJSON instead of TrashItems. TrashItems is the array you've populated, while TrashJson is the JSON encoded version of TrashItems.

Change

data: {TrashItems:TrashItems},

to..

data: {TrashItems:TrashJSON},

jQuery is correctly interpreting TrashItems as an array, and thus sending it as an array of values to the PHP script.

Alternatively, as Barmar has inferred in the comments, you could simply loop over the values array currently posted as TrashItems. You could do this using the following code.

foreach ($_POST['TrashItems'] as $TrashItem) {
    echo "$TrashItem\n";
}

This would output each item of the TrashItems array you originally passed in on a separate line, and provide the output of..

31
32
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