Ajax parsererror with JSON in Wordpress - php

Question

I'm doing an application web for a school and I'm stuck when trying to edit a student. I want the user to click in the row of and specific student and then open a form with his data.
I have to do an ajax request, so I can call my php function (the one which makes the query on my db) and load the data in the form. This is my jQuery code for the ajax request:
//When you click in the table students, in some element whose class is edit ...
$("#tblAlumnos").on("click", ".editar", function(event) {
var rowID = $(this).parents('tr').attr('id');
$.ajax({
type: 'POST',
url: '../ajax/',
data: {'table': 'alumnos', 'action': 'carga', 'ids': rowID},
dataType: 'json',
success: function(result) {
console.log(result.nombre);
},
error: function (jqXHR, exception) {
if (jqXHR.status === 0) {
alert('Not connect.\n Verify Network.');
} else if (jqXHR.status == 404) {
alert('Requested page not found. [404]');
} else if (jqXHR.status == 500) {
alert('Internal Server Error [500].');
} else if (exception === 'parsererror') {
alert('Requested JSON parse failed.');
alert(jqXHR.status);
alert(jqXHR);
} else if (exception === 'timeout') {
alert('Time out error.');
} else if (exception === 'abort') {
alert('Ajax request aborted.');
} else {
alert('Uncaught Error.\n' + jqXHR.responseText);
}
}
});
});
The ajax request calls the method to get the data from my db:
function cargaAlumno($ids) {
require 'db.php';
$sql = "SELECT * FROM Alumnos WHERE ID=$ids";
$result = $conexion->query($sql);
if ($result->num_rows > 0) {
$row = $result -> fetch_assoc();
$nombre = $row['Nombre'];
$apellidos = $row['Apellidos'];
$telefono = $row['Telefono'];
$usuario = $row['Usuario'];
$contrasena = $row['Contrasena'];
$result = array();
$result["nombre"] = $nombre;
$result["apellidos"] = $apellidos;
$result["telefono"] = $telefono;
$result["usuario"] = $usuario;
$result["contrasena"] = $contrasena;
ChromePhp::warn($result);
ChromePhp::warn(json_encode($result));
echo json_encode($result);
}
}
This method has to return a JSON to the ajax request, but the success method is never reached because of the error: parsererror.
I've tried with dataType: 'json' (this is when I have the error) and without it (it thinks its html). I also have tried with and without contentType and in my php: header('Content-type: application/json; charset=utf-8').
My json encoded looks like this:
{"nombre":"Susana","telefono":"56765336","usuario":"susa"}
I don't know if I need some more methods because I'm doing it in Wordpress or I have something wrong in my code.
Any help would be appreciated. Thank you in advance :)

Answer 1

If you are doing it in Wordpress, I'd use the built in wpdb to handle the db connection and results. Like so:
function cargaAlumno() {
global $wpdb;
$ids = $_POST['ids'];
$sql = $wpdb->get_results(
$wpdb->prepare("
SELECT *
FROM Alumnos
WHERE id = '$ids'
")
);
echo json_encode($sql);
exit();
}
Also remember this goes into your themes functions.php file.
Remember to hook it into the wp_ajax hook:
add_action( 'wp_ajax_nopriv_cargaAlumno', 'cargaAlumno' );
add_action( 'wp_ajax_cargaAlumno', 'cargaAlumno' );
Then in your ajax:
$("#tblAlumnos").on("click", ".editar", function(event) {
var rowID = $(this).parents('tr').attr('id');
$.ajax({
type: 'POST',
url: ajaxurl, //this is a wordpress ajaxurl hook
data: {'table': 'alumnos', 'action': 'cargaAlumno', 'ids': rowID}, // You didn't use the correct action name, it's your function name i.e. cargaAlumno
//dataType: 'json', dont need this
success: function(result) {
//Parse the data
var obj = jQuery.parseJSON(result);
console.log(obj[0].nombre); // I'm guessing nombre is your db column name
},
error: function (jqXHR, exception) {
if (jqXHR.status === 0) {
alert('Not connect.\n Verify Network.');
} else if (jqXHR.status == 404) {
alert('Requested page not found. [404]');
} else if (jqXHR.status == 500) {
alert('Internal Server Error [500].');
} else if (exception === 'parsererror') {
alert('Requested JSON parse failed.');
alert(jqXHR.status);
alert(jqXHR);
} else if (exception === 'timeout') {
alert('Time out error.');
} else if (exception === 'abort') {
alert('Ajax request aborted.');
} else {
alert('Uncaught Error.\n' + jqXHR.responseText);
}
}
});
});
This js file needs to be added into your theme to work in conjunction with the above reworked function()
Let me know if you need anymore help or have any other questions.

Answer 2

Not sure if you're only providing particular lines of your code or this is the whole thing, anyway this is definitely NOT how you should handle AJAX requests in WordPress:
You should use wp_ajax_ for actions that requires authentication or wp_ajax_nopriv_ for ones that doesn't
You should create an action for this function and send your request through admin-ajax.php using admin_url()
You should definitely secure your requests by creating nonces using wp_create_nonce() and verify it using wp_verify_nonce()
You should restrict direct access to your AJAX file while checking $_SERVER['HTTP_X_REQUESTED_WITH']
There's no need to require db.php since you're already working within functions.php and the db connection is already established.
Use the below method instead:
global $wpdb;
$query = "SELECT * FROM table_name";
$query_results = $wpdb->get_results($query);
To wrap it up, please follow the below structure:
Frontend (php file):
<?php
$ajax_nonce = wp_create_nonce("change_to_action_name");
$ajax_link = admin_url('admin-ajax.php?action=change_to_action_name&nonce=' . $ajax_nonce);
?>
<a class="do_ajax" href="#" data-ajax_link="<?php echo ajax_link; ?>" data-ajax_param="other_param">DO AJAX</a>
<input id="param" value="" />
Script File (js file):
$('.do_ajax').click(function () {
var ajax_link = $(this).attr('data-ajax_link');
var param = $(this).attr('data-ajax_param');
if (ajax_link && param) {
$.ajax({
type: "post",
dataType: "json",
url: ajax_link,
data: {
param: param,
},
success: function (response) {
if (response.type == "success") {
/*Get/updated returned vals from ajax*/
$('#param').val(response.new_param);
console.log('ajax was successful');
} else if (response.type == "error") {
console.log('ajax request had errors');
}else{
console.log('ajax request had errors');
}
}
});
} else {
console.log('ajax not sent');
}
});
Functions File (functions.php file):
add_action("wp_ajax_change_to_action_name", "change_to_action_name");
add_action("wp_ajax_nopriv_change_to_action_name", "change_to_action_name");
function change_to_action_name()
{
if (!wp_verify_nonce($_REQUEST['nonce'], "change_to_action_name")) {
exit("You think you are smart?");
}
$param = $_REQUEST['param'];
/*php actions goes here*/
$actions_success=0;
if($actions_success){
/*Query db and update vals here*/
$new_param = "new_val";
$result['new_param'] = $new_param;
$result['type'] = "success";
}else{
$result['type'] = "error";
}
if (!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
$result = json_encode($result);
echo $result;
} else {
header("Location: " . $_SERVER["HTTP_REFERER"]);
}
die();
}
Your current code contains many security flaws, so it's very recommended that you update it and use the above method.
Cheers!