下面是我的插件。将安装到wp-content

 <?php    // If this file is called directly, abort.
    namespace Booker;
    if ( ! defined( \'WPINC\' ) ) {
        die;
    }

 /**
 * Currently plugin version.
 * Start at version 1.0.0 and use SemVer - https://semver.org
 * Rename this for your plugin and update it as you release new versions.
 */
define( \'PLUGIN_NAME_VERSION\', \'1.0.0\' );

/**
 * The code that runs during plugin activation.
 * This action is documented in includes/class-booker-activator.php
 */
function activate_booker() {
    require_once plugin_dir_path(__FILE__) . \'includes/class-booker-activator.php\';
    error_log("Running Activation");
    Booker_Activator::activate();
}

/**
 * The code that runs during plugin deactivation.
 * This action is documented in includes/class-booker-deactivator.php
 */
function deactivate_booker() {
    require_once plugin_dir_path(__FILE__) . \'includes/class-booker-deactivator.php\';
    error_log("Running Deactivation");
    Booker_Deactivator::deactivate();
}

register_activation_hook( __FILE__, \'activate_booker\');
register_deactivation_hook( __FILE__, \'deactivate_booker\');

?>

它当然不会执行，但插件会按预期停用和激活。目前，这些函数中定义的函数调用中没有代码。。。。但缺少日志消息表明没有执行。然而，我遇到了一个问题：

该插件在激活期间生成了2368个字符的意外输出。如果您注意到“headers ready sent”消息、联合提要问题或其他问题，请尝试停用或删除此插件。

在我的日志中，我得到：

[08-Oct-2019 23:51:20 UTC] PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, function \'activate_booker\' not found or invalid function name in G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php on line 286
[08-Oct-2019 23:51:20 UTC] PHP Stack trace:
[08-Oct-2019 23:51:20 UTC] PHP   1. {main}() G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:0
[08-Oct-2019 23:51:20 UTC] PHP   2. activate_plugin() G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:44
[08-Oct-2019 23:51:20 UTC] PHP   3. do_action() G:\\wamp64\\www\\wordpress\\wp-admin\\includes\\plugin.php:672
[08-Oct-2019 23:51:20 UTC] PHP   4. WP_Hook->do_action() G:\\wamp64\\www\\wordpress\\wp-includes\\plugin.php:465
[08-Oct-2019 23:51:20 UTC] PHP   5. WP_Hook->apply_filters() G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php:310

还有

[09-Oct-2019 00:44:43 UTC] PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, function \'deactivate_booker\' not found or invalid function name in G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php on line 286
[09-Oct-2019 00:44:43 UTC] PHP Stack trace:
[09-Oct-2019 00:44:43 UTC] PHP   1. {main}() G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:0
[09-Oct-2019 00:44:43 UTC] PHP   2. deactivate_plugins($plugins = *uninitialized*, $silent = *uninitialized*, $network_wide = *uninitialized*) G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:192
[09-Oct-2019 00:44:43 UTC] PHP   3. do_action($tag = *uninitialized*, $arg = *uninitialized*) G:\\wamp64\\www\\wordpress\\wp-admin\\includes\\plugin.php:792
[09-Oct-2019 00:44:43 UTC] PHP   4. WP_Hook->do_action($args = *uninitialized*) G:\\wamp64\\www\\wordpress\\wp-includes\\plugin.php:465
[09-Oct-2019 00:44:43 UTC] PHP   5. WP_Hook->apply_filters($value = *uninitialized*, $args = *uninitialized*) G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php:310

更改函数名称时出现其他错误：

[09-Oct-2019 02:08:03 UTC] PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, function \'booker_deactivate\' not found or invalid function name in G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php on line 286
[09-Oct-2019 02:08:03 UTC] PHP Stack trace:
[09-Oct-2019 02:08:03 UTC] PHP   1. {main}() G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:0
[09-Oct-2019 02:08:03 UTC] PHP   2. deactivate_plugins() G:\\wamp64\\www\\wordpress\\wp-admin\\plugins.php:192
[09-Oct-2019 02:08:03 UTC] PHP   3. do_action() G:\\wamp64\\www\\wordpress\\wp-admin\\includes\\plugin.php:792
[09-Oct-2019 02:08:03 UTC] PHP   4. WP_Hook->do_action() G:\\wamp64\\www\\wordpress\\wp-includes\\plugin.php:465
[09-Oct-2019 02:08:03 UTC] PHP   5. WP_Hook->apply_filters() G:\\wamp64\\www\\wordpress\\wp-includes\\class-wp-hook.php:310

function my_plugin_activate_plugin() {
  ...
}

register_activation_hook( __FILE__, \'my_plugin_activate_plugin\' );

// Incorrect - These are referencing to global functions.
register_activation_hook( __FILE__, \'activate_booker\' );
register_deactivation_hook( __FILE__, \'deactivate_booker\' );

// Correct syntax when referencing to namespace functions.
register_activation_hook( __FILE__, \'Booker\\activate_booker\' );
register_deactivation_hook( __FILE__, \'Booker\\deactivate_booker\' );

// Or use the __NAMESPACE__ constant.
register_activation_hook( __FILE__, __NAMESPACE__ . \'\\activate_booker\' );
register_deactivation_hook( __FILE__, __NAMESPACE__ . \'\\deactivate_booker\' );