Wordpress admin-ajax.php - ajax

Question

I have a Wordpress admin-ajax.php problem:
First my WordPress admin-ajax.php returns 0 and now it's a clean sheet.
I already changed:
// Require an action parameter
if ( empty( $_REQUEST['action'] ) )
die( );
to
// Require an action parameter
if ($_REQUEST['action'] == 'crop_apply_header_image') {
var_dump($_REQUEST);
die();
My compleet admin-ajax.php:
<?php
/**
* WordPress Ajax Process Execution
*
* #package WordPress
* #subpackage Administration
*
* #link https://codex.wordpress.org/AJAX_in_Plugins
*/
/**
* Executing Ajax process.
*
* #since 2.1.0
*/
define( 'DOING_AJAX', true );
if ( ! defined( 'WP_ADMIN' ) ) {
define( 'WP_ADMIN', true );
}
/** Load WordPress Bootstrap */
require_once( dirname( dirname( __FILE__ ) ) . '/wp-load.php' );
/** Allow for cross-domain requests (from the front end). */
send_origin_headers();
// Require an action parameter
if ($_REQUEST['action'] == 'crop_apply_header_image') {
var_dump($_REQUEST);
die();
}
/** Load WordPress Administration APIs */
require_once( ABSPATH . 'wp-admin/includes/admin.php' );
/** Load Ajax Handlers for WordPress Core */
require_once( ABSPATH . 'wp-admin/includes/ajax-actions.php' );
#header( 'Content-Type: text/html; charset=' . get_option( 'blog_charset' ) );
#header( 'X-Robots-Tag: noindex' );
send_nosniff_header();
nocache_headers();
/** This action is documented in wp-admin/admin.php */
do_action( 'admin_init' );
$core_actions_get = array(
'fetch-list', 'ajax-tag-search', 'wp-compression-test', 'imgedit-preview', 'oembed-cache',
'autocomplete-user', 'dashboard-widgets', 'logged-in',
);
$core_actions_post = array(
'oembed-cache', 'image-editor', 'delete-comment', 'delete-tag', 'delete-link',
'delete-meta', 'delete-post', 'trash-post', 'untrash-post', 'delete-page', 'dim-comment',
'add-link-category', 'add-tag', 'get-tagcloud', 'get-comments', 'replyto-comment',
'edit-comment', 'add-menu-item', 'add-meta', 'add-user', 'closed-postboxes',
'hidden-columns', 'update-welcome-panel', 'menu-get-metabox', 'wp-link-ajax',
'menu-locations-save', 'menu-quick-search', 'meta-box-order', 'get-permalink',
'sample-permalink', 'inline-save', 'inline-save-tax', 'find_posts', 'widgets-order',
'save-widget', 'delete-inactive-widgets', 'set-post-thumbnail', 'date_format', 'time_format',
'wp-remove-post-lock', 'dismiss-wp-pointer', 'upload-attachment', 'get-attachment',
'query-attachments', 'save-attachment', 'save-attachment-compat', 'send-link-to-editor',
'send-attachment-to-editor', 'save-attachment-order', 'heartbeat', 'get-revision-diffs',
'save-user-color-scheme', 'update-widget', 'query-themes', 'parse-embed', 'set-attachment-thumbnail',
'parse-media-shortcode', 'destroy-sessions', 'install-plugin', 'update-plugin', 'press-this-save-post',
'press-this-add-category', 'crop-image', 'generate-password', 'save-wporg-username', 'delete-plugin',
'search-plugins', 'search-install-plugins', 'activate-plugin', 'update-theme', 'delete-theme',
'install-theme', 'get-post-thumbnail-html', 'get-community-events',
);
// Deprecated
$core_actions_post[] = 'wp-fullscreen-save-post';
// Register core Ajax calls.
if ( ! empty( $_GET['action'] ) && in_array( $_GET['action'], $core_actions_get ) )
add_action( 'wp_ajax_' . $_GET['action'], 'wp_ajax_' . str_replace( '-', '_', $_GET['action'] ), 1 );
if ( ! empty( $_POST['action'] ) && in_array( $_POST['action'], $core_actions_post ) )
add_action( 'wp_ajax_' . $_POST['action'], 'wp_ajax_' . str_replace( '-', '_', $_POST['action'] ), 1 );
add_action( 'wp_ajax_nopriv_heartbeat', 'wp_ajax_nopriv_heartbeat', 1 );
if ( is_user_logged_in() ) {
/**
* Fires authenticated Ajax actions for logged-in users.
*
* The dynamic portion of the hook name, `$_REQUEST['action']`,
* refers to the name of the Ajax action callback being fired.
*
* #since 2.1.0
*/
do_action( 'wp_ajax_' . $_REQUEST['action'] );
} else {
/**
* Fires non-authenticated Ajax actions for logged-out users.
*
* The dynamic portion of the hook name, `$_REQUEST['action']`,
* refers to the name of the Ajax action callback being fired.
*
* #since 2.8.0
*/
do_action( 'wp_ajax_nopriv_' . $_REQUEST['action'] );
}
// Default status
die( );
I tried the answers on stackoverflow but still no reaction. Can you help me please :)
Cheers,
Johan