我正在尝试开发一个简单的插件，但我遇到了一个问题：我有一个自定义插件WP_List_Table 在管理页面中，但当我单击“编辑行”或“删除行”之类的按钮时，它会执行一些预期的操作，并尝试使用刷新页面wp_redirect(). 这导致了一个问题：
Warning: Cannot modify header information - headers already sent by (output started at /opt/lampp/htdocs/wordpress/wp-includes/formatting.php:5652) in /opt/lampp/htdocs/wordpress/wp-includes/pluggable.php on line 1265
Warning: Cannot modify header information - headers already sent by (output started at /opt/lampp/htdocs/wordpress/wp-includes/formatting.php:5652) in /opt/lampp/htdocs/wordpress/wp-includes/pluggable.php on line 1268
我刚刚安装了高级自定义字段插件，我使用的是默认主题。目前，我的插件就是下面的代码（我在这里得到了它
https://www.sitepoint.com/using-wp_list_table-to-create-wordpress-admin-tables/):
if ( ! class_exists( \'WP_List_Table\' ) ) {
require_once( ABSPATH . \'wp-admin/includes/class-wp-list-table.php\' );
}
class Customers_List extends WP_List_Table {
/** Class constructor */
public function __construct() {
parent::__construct( [
\'singular\' => __( \'Customer\', \'sp\' ), //singular name of the listed records
\'plural\' => __( \'Customers\', \'sp\' ), //plural name of the listed records
\'ajax\' => false //does this table support ajax?
] );
}
/**
* Retrieve customers data from the database
*
* @param int $per_page
* @param int $page_number
*
* @return mixed
*/
public static function get_customers() {
$result = array();
$args = array(
\'role\' => \'Inscrito\',
);
$users = get_users( $args );
foreach($users as $user){
$user_form = \'user_\'. $user->ID;
$image = get_field(\'receipt\', $user_form);
$size = \'full\'; // (thumbnail, medium, large, full or custom size)
if( $image ) {
$image_url = \'<a href="\' .$image[\'url\'] . \'"> a </a>\';
}else{
$image_url = \'False\';
}
array_push($result,
array( \'ID\' => $user->ID,
\'name\' => $user->status,
\'address\' => $image_url,
\'city\' => $image_url,
)
);
}
return $result;
}
/**
* Delete a customer record.
*
* @param int $id customer ID
*/
public static function delete_customer( $id ) {
global $wpdb;
$wpdb->delete(
"{$wpdb->prefix}customers",
[ \'ID\' => $id ],
[ \'%d\' ]
);
}
/** Text displayed when no customer data is available */
public function no_items() {
_e( \'No customers avaliable.\', \'sp\' );
}
/**
* Render a column when no column specific method exist.
*
* @param array $item
* @param string $column_name
*
* @return mixed
*/
public function column_default( $item, $column_name ) {
switch ( $column_name ) {
case \'address\':
case \'city\':
return $item[ $column_name ];
default:
return print_r( $item, true ); //Show the whole array for troubleshooting purposes
}
}
/**
* Render the bulk edit checkbox
*
* @param array $item
*
* @return string
*/
function column_cb( $item ) {
return sprintf(
\'<input type="checkbox" name="bulk-delete[]" value="%s" />\', $item[\'ID\']
);
}
/**
* Method for name column
*
* @param array $item an array of DB data
*
* @return string
*/
function column_name( $item ) {
$delete_nonce = wp_create_nonce( \'sp_delete_customer\' );
$title = \'<strong>\' . $item[\'name\'] . \'</strong>\';
$actions = [
\'delete\' => sprintf( \'<a href="?page=%s&action=%s&customer=%s&_wpnonce=%s">Delete</a>\', esc_attr( $_REQUEST[\'page\'] ), \'delete\', absint( $item[\'ID\'] ), $delete_nonce )
];
return $title . $this->row_actions( $actions );
}
/**
* Associative array of columns
*
* @return array
*/
function get_columns() {
$columns = [
\'cb\' => \'<input type="checkbox" />\',
\'name\' => __( \'Name\', \'sp\' ),
\'address\' => __( \'Address\', \'sp\' ),
\'city\' => __( \'City\', \'sp\' )
];
return $columns;
}
/**
* Columns to make sortable.
*
* @return array
*/
public function get_sortable_columns() {
$sortable_columns = array(
\'name\' => array( \'name\', true ),
\'city\' => array( \'city\', false )
);
return $sortable_columns;
}
/**
* Returns an associative array containing the bulk action
*
* @return array
*/
public function get_bulk_actions() {
$actions = [
\'bulk-delete\' => \'Delete\'
];
return $actions;
}
/**
* Handles data query and filter, sorting, and pagination.
*/
public function prepare_items() {
$this->_column_headers = $this->get_column_info();
/** Process bulk action */
$this->process_bulk_action();
$users = self::get_customers();
$per_page = $this->get_items_per_page( \'customers_per_page\', 5 );
$current_page = $this->get_pagenum();
$total_items = self::record_count();
$slice_offset = ( ( $current_page-1 )* $per_page );
$slice_limit = $slice_offset+$per_page;
// only ncessary because we have sample data
$found_data = array_slice( $users, $slice_offset, $slice_limit);
$this->set_pagination_args( [
\'total_items\' => $total_items, //WE have to calculate the total number of items
\'per_page\' => $per_page //WE have to determine how many items to show on a page
] );
$this->items = $found_data;
}
public function process_bulk_action() {
//Detect when a bulk action is being triggered...
if ( \'delete\' === $this->current_action() ) {
// In our file that handles the request, verify the nonce.
$nonce = esc_attr( $_REQUEST[\'_wpnonce\'] );
if ( ! wp_verify_nonce( $nonce, \'sp_delete_customer\' ) ) {
die( \'Go get a life script kiddies\' );
}
else {
self::delete_customer( absint( $_GET[\'customer\'] ) );
// esc_url_raw() is used to prevent converting ampersand in url to "#038;"
// add_query_arg() return the current url
wp_redirect( esc_url_raw(add_query_arg()) );
exit;
}
}
// If the delete bulk action is triggered
if ( ( isset( $_POST[\'action\'] ) && $_POST[\'action\'] == \'bulk-delete\' )
|| ( isset( $_POST[\'action2\'] ) && $_POST[\'action2\'] == \'bulk-delete\' )
) {
$delete_ids = esc_sql( $_POST[\'bulk-delete\'] );
// loop over the array of record IDs and delete them
foreach ( $delete_ids as $id ) {
self::delete_customer( $id );
}
// esc_url_raw() is used to prevent converting ampersand in url to "#038;"
// add_query_arg() return the current url
wp_redirect( esc_url_raw(add_query_arg()) );
exit;
}
}
}
class SP_Plugin {
// class instance
static $instance;
// customer WP_List_Table object
public $customers_obj;
// class constructor
public function __construct() {
add_filter( \'set-screen-option\', [ __CLASS__, \'set_screen\' ], 10, 3 );
add_action( \'admin_menu\', [ $this, \'plugin_menu\' ] );
}
public static function set_screen( $status, $option, $value ) {
return $value;
}
public function plugin_menu() {
$hook = add_menu_page(
\'Sitepoint WP_List_Table Example\',
\'SP WP_List_Table\',
\'manage_options\',
\'wp_list_table_class\',
[ $this, \'plugin_settings_page\' ]
);
add_action( "load-$hook", [ $this, \'screen_option\' ] );
}
/**
* Plugin settings page
*/
public function plugin_settings_page() {
?>
<div class="wrap">
<h2>WP_List_Table Class Example</h2>
<div id="poststuff">
<div id="post-body" class="metabox-holder columns-2">
<div id="post-body-content">
<div class="meta-box-sortables ui-sortable">
<form method="post">
<?php
$this->customers_obj->prepare_items();
$this->customers_obj->display(); ?>
</form>
</div>
</div>
</div>
<br class="clear">
</div>
</div>
<?php
}
/**
* Screen options
*/
public function screen_option() {
$option = \'per_page\';
$args = [
\'label\' => \'Customers\',
\'default\' => 5,
\'option\' => \'customers_per_page\'
];
add_screen_option( $option, $args );
$this->customers_obj = new Customers_List();
}
/** Singleton instance */
public static function get_instance() {
if ( ! isset( self::$instance ) ) {
self::$instance = new self();
}
return self::$instance;
}
}
add_action( \'plugins_loaded\', function () {
SP_Plugin::get_instance();
} );
我知道这是一个经常被问到的问题，但我在问之前试着搜索了很多，但没有任何帮助。
