Question: I'm working on a search plugin for the front-end of a Wordpress site. At the moment I keep getting a 400 Bad Request Error and I can't understand why. I've reviewed many questions on SO and the WordpressStackExchange but cannot see where I'm going wrong, nothing appears to be out of place. Please give me guidance:

plugin.php:

```
function my_admin_scripts() {
    $localize = array(
        'ajaxurl' => admin_url( 'admin-ajax.php' )
    );

    wp_register_script('veh-app-search', plugin_dir_url( __FILE__ ) . '/ajax.js', '', '', true);

    wp_localize_script( 'veh-app-search', 'veh_app_script', $localize);

    wp_enqueue_script( 'veh-app-search', plugin_dir_url( __FILE__ ) . '/ajax.js', array( 'jquery' ) );
}  

add_action( 'wp_enqueue_scripts', 'my_admin_scripts' );
add_action( 'wp_ajax_the_ajax_hook', 'handle_request' );
add_action( 'wp_ajax_nopriv_the_ajax_hook', 'handle_request' ); 

    //takes care of the $_POST data
function handle_request(){
    echo "hello";
}

```

ajax.js 

```
    var data = {
        action: 'handle_request',
        RequestType: 'category',
        Category:  jQuery('#Category option:selected').val()
    };

    jQuery.post(
        veh_app_script.ajaxurl,
        data,
        function(categories){
            console.log(categories);
        }
    );

```

One would expect to see "Hello" in the console but I only see the error in the console:

```
jquery.js?ver=1.12.4:4 POST http://localhost/wp-admin/admin-ajax.php 400 (Bad Request)

```

Answer: 
Please replace code and check

plugin.php

```
function my_admin_scripts() {
    $localize = array(
        'ajaxurl' => admin_url( 'admin-ajax.php' )
    );

    wp_enqueue_script( 'veh-app-search', plugin_dir_url( __FILE__ ) . '/ajax.js', array( 'jquery' ) );

    wp_localize_script( 'veh-app-search', 'veh_app_script', $localize);

}  

add_action( 'wp_enqueue_scripts', 'my_admin_scripts' );
add_action( 'wp_ajax_handle_request', 'handle_request' );
add_action( 'wp_ajax_nopriv_handle_request', 'handle_request' ); 

    //takes care of the $_POST data
function handle_request(){
    echo "hello";
}

```

ajax.js

```
var data = {
        action: 'handle_request',
        RequestType: 'category',
        Category:  jQuery('#Category option:selected').val()
    };

    jQuery.post(
        veh_app_script.ajaxurl,
        data,
        function(categories){
            console.log(categories);
        }
    );

```
Use JSON instead:

```
function handle_request(){
  echo json_encode( array( "message" => "hello" ) );
  exit;
}

```

Parse the JSON in your `ajax.js` response handler:

```
function( response ) {
  var returndata = JSON.parse( response );
  console.log( returndata.message );
}

```

Don't forget to add `json2` as a dependency to your script.

```
wp_enqueue_script( 'veh-app-search', plugin_dir_url( __FILE__ ) . '/ajax.js', array( 'jquery', 'json2' ) );

```