Title: Plugin development admin-ajax.php error 400?
Last modified: February 9, 2018

---

# Plugin development admin-ajax.php error 400?

 *  [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/)
 * I’m writing a plugin that should use ajax.
    Here’s my part of the main file of
   the plugin:
 *     ```
       add_action( 'wp_enqueue_scripts', 'fhw_register_script' );
   
       function fhw_register_script() {
       	wp_deregister_script( 'jquery' );
       	add_action( 'wp_ajax_fhw_do_ajax_request', 'fhw_do_ajax_request' );
   
       	wp_register_script( 'jquery', 'http://code.jquery.com/jquery-latest.min.js');
       	wp_register_script( 'fhw_formular', plugins_url( '/js/formular.js', __FILE__ ), array( 'jquery' ) );
   
       	wp_enqueue_script( 'fhw_formular' );
   
       	wp_localize_script( 'fhw_formular', 'ajax_object',
                   array( 'ajax_url' => admin_url( 'admin-ajax.php' ), 'we_value' => 1234 ) );
   
       	wp_enqueue_script( 'jquery' );
       }
       ```
   
 * So if I call the formular.js my dev-console says
 * > Filed to load resource: the server responded with a status of 400 (Bad Request)
 *  for the File admin-ajax.php. What to do?

Viewing 12 replies - 1 through 12 (of 12 total)

 *  [Jacob Peattie](https://wordpress.org/support/users/jakept/)
 * (@jakept)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9956406)
 * Where’s the actual AJAX call? Or the code hooked to respond to it? What you’ve
   got here won’t request admin-ajax.php from the front-end on its own, so couldn’t
   be causing the error.
 * Also, [don’t load your own jQuery](https://pippinsplugins.com/why-loading-your-own-jquery-is-irresponsible/).
 * And you don’t need that last call to enqueue it. It’s already happening as a 
   dependency of your script.
    -  This reply was modified 8 years, 2 months ago by [Jacob Peattie](https://wordpress.org/support/users/jakept/).
 *  Thread Starter [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9956590)
 * Alright, this is my code how I am calling it
 *     ```
       jQuery(document).ready( function($) {
   
       	$('input').bind("change", function(e) {
       		onSelect();
       	});
   
   
       });
   
       function onSelect() {
       	var data = {
       		'action': 'fhw_getTyp',
       		'typ' : this.value
       	};
       	jQuery.post(ajax_object.ajax_url, data, function(response) {
       		$(".ergebnis").html(response);
       	});
       };
       ```
   
    -  This reply was modified 8 years, 2 months ago by [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/).
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9961222)
 * Move your add action call to ‘wp_ajax_fhw_do_ajax_request’ to outside the enqueue
   scripts callback. admin-ajax.php requests do not try to enqueue scripts. Your
   add action call can execute on plugin load, it does not need to be in a callback.
 *  Thread Starter [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9961597)
 * > Move your add action call to ‘wp_ajax_fhw_do_ajax_request’ to outside the enqueue
   > scripts callback. admin-ajax.php requests do not try to enqueue scripts. Your
   > add action call can execute on plugin load, it does not need to be in a callback.
 * As I understand, I should use this code like so
 *     ```
       add_action( 'wp_enqueue_scripts', 'fhw_register_script' );
       add_action( 'wp_ajax_fhw_do_ajax_request', 'fhw_do_ajax_request' );
       function fhw_register_script() {
       	wp_register_script( 'fhw_formular', plugins_url( '/js/formular.js', __FILE__ ), array( 'jquery' ) );
   
       	wp_enqueue_script( 'fhw_formular' );
   
       	wp_localize_script( 'fhw_formular', 'ajax_object',
                   array( 'ajax_url' => admin_url( 'admin-ajax.php' ), 'we_value' => 1234 ) );
       	wp_enqueue_script( 'fhw_formular' );
       }
       ```
   
 * The 400 Bad Request error persists.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9962948)
 * Yes, that was my intention. But I missed another important detail. Please change
   that one line to this:
    `add_action( 'wp_ajax_fhw_getTyp', 'fhw_do_ajax_request');`
   The action tag has to correspond to the action data passed from jQuery, not your
   callback name.
 * You probably know this, but it’s worth noting that one must be logged in for 
   that action to work. For non-logged in users, the action tag would be ‘wp_ajax_no_priv_fhw_getTyp’,
   added separately.
 *  Thread Starter [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9963988)
 * > Yes, that was my intention. But I missed another important detail. Please change
   > that one line to this:
   >  add_action( ‘wp_ajax_fhw_getTyp’, ‘fhw_do_ajax_request’);
   > The action tag has to correspond to the action data passed from jQuery, not
   > your callback name.
   > You probably know this, but it’s worth noting that one must be logged in for
   > that action to work. For non-logged in users, the action tag would be ‘wp_ajax_no_priv_fhw_getTyp’,
   > added separately.
 * Ok, I did it like this:
 *     ```
       add_action( 'wp_ajax_fhw_ladeMarke', 'fhw_do_ajax_request' );
       add_action( 'wp_ajax_no_priv_fhw_ladeMarke', 'fhw_do_ajax_request' );
   
       function fhw_register_script() {
       	wp_register_script( 'fhw_formular', plugins_url( '/js/formular.js', __FILE__ ), array( 'jquery' ) );
   
       	wp_enqueue_script( 'fhw_formular' );
   
       	wp_localize_script( 'fhw_formular', 'ajax_object',
                   array( 'ajax_url' => admin_url( 'admin-ajax.php' ), 'we_value' => 1234 ) );
       	wp_enqueue_script( 'fhw_formular' );
       }
       ```
   
 * But that is also not working, still the same 400 Error.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9966338)
 * I’m assuming the wp_enqueue_scripts add action still exists for fhw_register_script()
   somewhere. And apparently the action value from your jQuery is now fhw_ladeMarke
   instead of fhw_getTyp like in the snippet posted in your first reply to Jacob?
 * Let’s be sure the Ajax callback is getting called. It should be if the above 
   is true. Place something like `error_log('Notice: fhw_do_ajax_request() was called');`
   as the first line in fhw_do_ajax_request(). Do a test, then verify the message
   appears in the error log. Whether it exists or not will tell us what direction
   to look for problems.
 *  Thread Starter [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9968504)
 * > I’m assuming the wp_enqueue_scripts add action still exists for fhw_register_script()
   > somewhere.
 * The script above is the actual, whole plugin main file.
 * > And apparently the action value from your jQuery is now fhw_ladeMarke instead
   > of fhw_getTyp like in the snippet posted in your first reply to Jacob?
 * I just renamed that, but in all files.
 * > Let’s be sure the Ajax callback is getting called. It should be if the above
   > is true. Place something like error_log(‘Notice: fhw_do_ajax_request() was 
   > called’); as the first line in fhw_do_ajax_request(). Do a test, then verify
   > the message appears in the error log. Whether it exists or not will tell us
   > what direction to look for problems.
 * Ehm.. should I have a fhw_do_ajax_request function? What should it contain? As
   said, the script in the reply above is my whole file (without comments). Oh, 
   there is a addaction more to enqueue fhw_register_script() too.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9970867)
 * Yes! You need a fhw_do_ajax_request() function because you have `add_action( '
   wp_ajax_fhw_ladeMarke', 'fhw_do_ajax_request' );`
    That is the function that 
   handles your Ajax request server side. I don’t know what your Ajax call is supposed
   to accomplish on the server, but that function is key to making it happen.
 * When you do
 *     ```
       jQuery.post(ajax_object.ajax_url, data, function(response) {
       		$(".ergebnis").html(response);
       });
       ```
   
 * a request is POSTed to ajax_url, which is the admin-ajax.php file. That file 
   grabs the action value (‘fhw_ladeMarke’) from the passed data array and appends
   it to “wp_ajax_” to arrive at the action tag to which you added ‘fhw_do_ajax_request’.
   The admin-ajax.php file then executes
    `do_action( 'wp_ajax_fhw_ladeMarke', '
   fhw_do_ajax_request' );` which calls your fhw_do_ajax_request() function to handle
   the Ajax request. Note the initial **do** instead of **add**. It’s a major distinction.
 * I hope that makes sense. Understanding it is essential to understanding how Ajax
   in WP works. You should consider the process until it truly makes sense to you.
   It might not resolve your immediate 400 problem, but it’s just as important for
   resolving similar issues in the future. If you need clarification on any point,
   just ask. I’ll do my best to help your understanding.
 *  Thread Starter [fhwebdesign](https://wordpress.org/support/users/fhwebdesign/)
 * (@fhwebdesign)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9972485)
 * Okay, thank you for that good explanation! The mistake was that I forgot to include
   the ladeMarke.php into the plugins main file. Thanks for your help!
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [8 years, 2 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-9974287)
 * Hah! Those dependencies! I’m glad you tracked down the problem.
 *  [ikirby](https://wordpress.org/support/users/ikirby/)
 * (@ikirby)
 * [7 years, 11 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-10228340)
 * Thank you! You saved my day!!!
    I had the same problem – new version of plugin
   was not included :)))))))))))

Viewing 12 replies - 1 through 12 (of 12 total)

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## Tags

 * [ajax](https://wordpress.org/support/topic-tag/ajax/)

 * In: [Developing with WordPress](https://wordpress.org/support/forum/wp-advanced/)
 * 12 replies
 * 4 participants
 * Last reply from: [ikirby](https://wordpress.org/support/users/ikirby/)
 * Last activity: [7 years, 11 months ago](https://wordpress.org/support/topic/plugin-development-admin-ajax-php-error-400/#post-10228340)
 * Status: not resolved

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