do_action( $args );

	array_pop( $wp_current_filter );
}

/**
 * Retrieve the number of times an action is fired.
 *
 * @since 2.1.0
 *
 * @global array $wp_actions Increments the amount of times action was triggered.
 *
 * @param string $tag The name of the action hook.
 * @return int The number of times action hook $tag is fired.
 */
function did_action( $tag ) {
	global $wp_actions;

	if ( ! isset( $wp_actions[ $tag ] ) ) {
		return 0;
	}

	return $wp_actions[ $tag ];
}

/**
 * Execute functions hooked on a specific action hook, specifying arguments in an array.
 *
 * @since 2.1.0
 *
 * @see do_action() This function is identical, but the arguments passed to the
 *                  functions hooked to $tag< are supplied using an array.
 * @global array $wp_filter         Stores all of the filters
 * @global array $wp_actions        Increments the amount of times action was triggered.
 * @global array $wp_current_filter Stores the list of current filters with the current one last
 *
 * @param string $tag  The name of the action to be executed.
 * @param array  $args The arguments supplied to the functions hooked to `$tag`.
 */
function do_action_ref_array( $tag, $args ) {
	global $wp_filter, $wp_actions, $wp_current_filter;

	if ( ! isset( $wp_actions[ $tag ] ) ) {
		$wp_actions[ $tag ] = 1;
	} else {
		++$wp_actions[ $tag ];
	}

	// Do 'all' actions first
	if ( isset( $wp_filter['all'] ) ) {
		$wp_current_filter[] = $tag;
		$all_args            = func_get_args();
		_wp_call_all_hook( $all_args );
	}

	if ( ! isset( $wp_filter[ $tag ] ) ) {
		if ( isset( $wp_filter['all'] ) ) {
			array_pop( $wp_current_filter );
		}
		return;
	}

	if ( ! isset( $wp_filter['all'] ) ) {
		$wp_current_filter[] = $tag;
	}

	$wp_filter[ $tag ]->do_action( $args );

	array_pop( $wp_current_filter );
}

/**
 * Check if any action has been registered for a hook.
 *
 * @since 2.5.0
 *
 * @see has_filter() has_action() is an alias of has_filter().
 *
 * @param string        $tag               The name of the action hook.
 * @param callable|bool $function_to_check Optional. The callback to check for. Default false.
 * @return bool|int If $function_to_check is omitted, returns boolean for whether the hook has
 *                  anything registered. When checking a specific function, the priority of that
 *                  hook is returned, or false if the function is not attached. When using the
 *                  $function_to_check argument, this function may return a non-boolean value
 *                  that evaluates to false (e.g.) 0, so use the === operator for testing the
 *                  return value.
 */
function has_action( $tag, $function_to_check = false ) {
	return has_filter( $tag, $function_to_check );
}

/**
 * Removes a function from a specified action hook.
 *
 * This function removes a function attached to a specified action hook. This
 * method can be used to remove default functions attached to a specific filter
 * hook and possibly replace them with a substitute.
 *
 * @since 1.2.0
 *
 * @param string   $tag                The action hook to which the function to be removed is hooked.
 * @param callable $function_to_remove The name of the function which should be removed.
 * @param int      $priority           Optional. The priority of the function. Default 10.
 * @return bool Whether the function is removed.
 */
function remove_action( $tag, $function_to_remove, $priority = 10 ) {
	return remove_filter( $tag, $function_to_remove, $priority );
}

/**
 * Remove all of the hooks from an action.
 *
 * @since 2.7.0
 *
 * @param string   $tag      The action to remove hooks from.
 * @param int|bool $priority The priority number to remove them from. Default false.
 * @return true True when finished.
 */
function remove_all_actions( $tag, $priority = false ) {
	return remove_all_filters( $tag, $priority );
}

/**
 * Fires functions attached to a deprecated filter hook.
 *
 * When a filter hook is deprecated, the apply_filters() call is replaced with
 * apply_filters_deprecated(), which triggers a deprecation notice and then fires
 * the original filter hook.
 *
 * Note: the value and extra arguments passed to the original apply_filters() call
 * must be passed here to `$args` as an array. For example:
 *
 *     // Old filter.
 *     return apply_filters( 'wpdocs_filter', $value, $extra_arg );
 *
 *     // Deprecated.
 *     return apply_filters_deprecated( 'wpdocs_filter', array( $value, $extra_arg ), '4.9', 'wpdocs_new_filter' );
 *
 * @since 4.6.0
 *
 * @see _deprecated_hook()
 *
 * @param string $tag         The name of the filter hook.
 * @param array  $args        Array of additional function arguments to be passed to apply_filters().
 * @param string $version     The version of WordPress that deprecated the hook.
 * @param string $replacement Optional. The hook that should have been used. Default false.
 * @param string $message     Optional. A message regarding the change. Default null.
 */
function apply_filters_deprecated( $tag, $args, $version, $replacement = false, $message = null ) {
	if ( ! has_filter( $tag ) ) {
		return $args[0];
	}

	_deprecated_hook( $tag, $version, $replacement, $message );

	return apply_filters_ref_array( $tag, $args );
}

/**
 * Fires functions attached to a deprecated action hook.
 *
 * When an action hook is deprecated, the do_action() call is replaced with
 * do_action_deprecated(), which triggers a deprecation notice and then fires
 * the original hook.
 *
 * @since 4.6.0
 *
 * @see _deprecated_hook()
 *
 * @param string $tag         The name of the action hook.
 * @param array  $args        Array of additional function arguments to be passed to do_action().
 * @param string $version     The version of WordPress that deprecated the hook.
 * @param string $replacement Optional. The hook that should have been used.
 * @param string $message     Optional. A message regarding the change.
 */
function do_action_deprecated( $tag, $args, $version, $replacement = false, $message = null ) {
	if ( ! has_action( $tag ) ) {
		return;
	}

	_deprecated_hook( $tag, $version, $replacement, $message );

	do_action_ref_array( $tag, $args );
}

//
// Functions for handling plugins.
//

/**
 * Gets the basename of a plugin.
 *
 * This method extracts the name of a plugin from its filename.
 *
 * @since 1.5.0
 *
 * @global array $wp_plugin_paths
 *
 * @param string $file The filename of plugin.
 * @return string The name of a plugin.
 */
function plugin_basename( $file ) {
	global $wp_plugin_paths;

	// $wp_plugin_paths contains normalized paths.
	$file = wp_normalize_path( $file );

	arsort( $wp_plugin_paths );
	foreach ( $wp_plugin_paths as $dir => $realdir ) {
		if ( strpos( $file, $realdir ) === 0 ) {
			$file = $dir . substr( $file, strlen( $realdir ) );
		}
	}

	$plugin_dir    = wp_normalize_path( WP_PLUGIN_DIR );
	$mu_plugin_dir = wp_normalize_path( WPMU_PLUGIN_DIR );

	$file = preg_replace( '#^' . preg_quote( $plugin_dir, '#' ) . '/|^' . preg_quote( $mu_plugin_dir, '#' ) . '/#', '', $file ); // get relative path from plugins dir
	$file = trim( $file, '/' );
	return $file;
}

/**
 * Register a plugin's real path.
 *
 * This is used in plugin_basename() to resolve symlinked paths.
 *
 * @since 3.9.0
 *
 * @see wp_normalize_path()
 *
 * @global array $wp_plugin_paths
 *
 * @staticvar string $wp_plugin_path
 * @staticvar string $wpmu_plugin_path
 *
 * @param string $file Known path to the file.
 * @return bool Whether the path was able to be registered.
 */
function wp_register_plugin_realpath( $file ) {
	global $wp_plugin_paths;

	// Normalize, but store as static to avoid recalculation of a constant value
	static $wp_plugin_path = null, $wpmu_plugin_path = null;
	if ( ! isset( $wp_plugin_path ) ) {
		$wp_plugin_path   = wp_normalize_path( WP_PLUGIN_DIR );
		$wpmu_plugin_path = wp_normalize_path( WPMU_PLUGIN_DIR );
	}

	$plugin_path     = wp_normalize_path( dirname( $file ) );
	$plugin_realpath = wp_normalize_path( dirname( realpath( $file ) ) );

	if ( $plugin_path === $wp_plugin_path || $plugin_path === $wpmu_plugin_path ) {
		return false;
	}

	if ( $plugin_path !== $plugin_realpath ) {
		$wp_plugin_paths[ $plugin_path ] = $plugin_realpath;
	}

	return true;
}

/**
 * Get the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in.
 *
 * @since 2.8.0
 *
 * @param string $file The filename of the plugin (__FILE__).
 * @return string the filesystem path of the directory that contains the plugin.
 */
function plugin_dir_path( $file ) {
	return trailingslashit( dirname( $file ) );
}

/**
 * Get the URL directory path (with trailing slash) for the plugin __FILE__ passed in.
 *
 * @since 2.8.0
 *
 * @param string $file The filename of the plugin (__FILE__).
 * @return string the URL path of the directory that contains the plugin.
 */
function plugin_dir_url( $file ) {
	return trailingslashit( plugins_url( '', $file ) );
}

/**
 * Set the activation hook for a plugin.
 *
 * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
 * called. In the name of this hook, PLUGINNAME is replaced with the name
 * of the plugin, including the optional subdirectory. For example, when the
 * plugin is located in wp-content/plugins/sampleplugin/sample.php, then
 * the name of this hook will become 'activate_sampleplugin/sample.php'.
 *
 * When the plugin consists of only one file and is (as by default) located at
 * wp-content/plugins/sample.php the name of this hook will be
 * 'activate_sample.php'.
 *
 * @since 2.0.0
 *
 * @param string   $file     The filename of the plugin including the path.
 * @param callable $function The function hooked to the 'activate_PLUGIN' action.
 */
function register_activation_hook( $file, $function ) {
	$file = plugin_basename( $file );
	add_action( 'activate_' . $file, $function );
}

/**
 * Set the deactivation hook for a plugin.
 *
 * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
 * called. In the name of this hook, PLUGINNAME is replaced with the name
 * of the plugin, including the optional subdirectory. For example, when the
 * plugin is located in wp-content/plugins/sampleplugin/sample.php, then
 * the name of this hook will become 'deactivate_sampleplugin/sample.php'.
 *
 * When the plugin consists of only one file and is (as by default) located at
 * wp-content/plugins/sample.php the name of this hook will be
 * 'deactivate_sample.php'.
 *
 * @since 2.0.0
 *
 * @param string   $file     The filename of the plugin including the path.
 * @param callable $function The function hooked to the 'deactivate_PLUGIN' action.
 */
function register_deactivation_hook( $file, $function ) {
	$file = plugin_basename( $file );
	add_action( 'deactivate_' . $file, $function );
}

/**
 * Set the uninstallation hook for a plugin.
 *
 * Registers the uninstall hook that will be called when the user clicks on the
 * uninstall link that calls for the plugin to uninstall itself. The link won't
 * be active unless the plugin hooks into the action.
 *
 * The plugin should not run arbitrary code outside of functions, when
 * registering the uninstall hook. In order to run using the hook, the plugin
 * will have to be included, which means that any code laying outside of a
 * function will be run during the uninstallation process. The plugin should not
 * hinder the uninstallation process.
 *
 * If the plugin can not be written without running code within the plugin, then
 * the plugin should create a file named 'uninstall.php' in the base plugin
 * folder. This file will be called, if it exists, during the uninstallation process
 * bypassing the uninstall hook. The plugin, when using the 'uninstall.php'
 * should always check for the 'WP_UNINSTALL_PLUGIN' constant, before
 * executing.
 *
 * @since 2.7.0
 *
 * @param string   $file     Plugin file.
 * @param callable $callback The callback to run when the hook is called. Must be
 *                           a static method or function.
 */
function register_uninstall_hook( $file, $callback ) {
	if ( is_array( $callback ) && is_object( $callback[0] ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'Only a static class method or function can be used in an uninstall hook.' ), '3.1.0' );
		return;
	}

	/*
	 * The option should not be autoloaded, because it is not needed in most
	 * cases. Emphasis should be put on using the 'uninstall.php' way of
	 * uninstalling the plugin.
	 */
	$uninstallable_plugins                             = (array) get_option( 'uninstall_plugins' );
	$uninstallable_plugins[ plugin_basename( $file ) ] = $callback;

	update_option( 'uninstall_plugins', $uninstallable_plugins );
}

/**
 * Call the 'all' hook, which will process the functions hooked into it.
 *
 * The 'all' hook passes all of the arguments or parameters that were used for
 * the hook, which this function was called for.
 *
 * This function is used internally for apply_filters(), do_action(), and
 * do_action_ref_array() and is not meant to be used from outside those
 * functions. This function does not check for the existence of the all hook, so
 * it will fail unless the all hook exists prior to this function call.
 *
 * @since 2.5.0
 * @access private
 *
 * @global array $wp_filter  Stores all of the filters
 *
 * @param array $args The collected parameters from the hook that was called.
 */
function _wp_call_all_hook( $args ) {
	global $wp_filter;

	$wp_filter['all']->do_all_hook( $args );
}

/**
 * Build Unique ID for storage and retrieval.
 *
 * The old way to serialize the callback caused issues and this function is the
 * solution. It works by checking for objects and creating a new property in
 * the class to keep track of the object and new objects of the same class that
 * need to be added.
 *
 * It also allows for the removal of actions and filters for objects after they
 * change class properties. It is possible to include the property $wp_filter_id
 * in your class and set it to "null" or a number to bypass the workaround.
 * However this will prevent you from adding new classes and any new classes
 * will overwrite the previous hook by the same class.
 *
 * Functions and static method callbacks are just returned as strings and
 * shouldn't have any speed penalty.
 *
 * @link https://core.trac.wordpress.org/ticket/3875
 *
 * @since 2.2.3
 * @access private
 *
 * @global array $wp_filter Storage for all of the filters and actions.
 * @staticvar int $filter_id_count
 *
 * @param string   $tag      Used in counting how many hooks were applied
 * @param callable $function Used for creating unique id
 * @param int|bool $priority Used in counting how many hooks were applied. If === false
 *                           and $function is an object reference, we return the unique
 *                           id only if it already has one, false otherwise.
 * @return string|false Unique ID for usage as array key or false if $priority === false
 *                      and $function is an object reference, and it does not already have
 *                      a unique id.
 */
function _wp_filter_build_unique_id( $tag, $function, $priority ) {
	global $wp_filter;
	static $filter_id_count = 0;

	if ( is_string( $function ) ) {
		return $function;
	}

	if ( is_object( $function ) ) {
		// Closures are currently implemented as objects
		$function = array( $function, '' );
	} else {
		$function = (array) $function;
	}

	if ( is_object( $function[0] ) ) {
		// Object Class Calling
		if ( function_exists( 'spl_object_hash' ) ) {
			return spl_object_hash( $function[0] ) . $function[1];
		} else {
			$obj_idx = get_class( $function[0] ) . $function[1];
			if ( ! isset( $function[0]->wp_filter_id ) ) {
				if ( false === $priority ) {
					return false;
				}
				$obj_idx                  .= isset( $wp_filter[ $tag ][ $priority ] ) ? count( (array) $wp_filter[ $tag ][ $priority ] ) : $filter_id_count;
				$function[0]->wp_filter_id = $filter_id_count;
				++$filter_id_count;
			} else {
				$obj_idx .= $function[0]->wp_filter_id;
			}

			return $obj_idx;
		}
	} elseif ( is_string( $function[0] ) ) {
		// Static Calling
		return $function[0] . '::' . $function[1];
	}
}
<br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined function apply_filters() in /srv/users/serverpilot/apps/cryotshock/public/wp-includes/error-protection.php:119
Stack trace:
#0 /srv/users/serverpilot/apps/cryotshock/public/wp-includes/error-protection.php(83): wp_is_fatal_error_handler_enabled()
#1 /srv/users/serverpilot/apps/cryotshock/public/wp-settings.php(52): wp_register_fatal_error_handler()
#2 /srv/users/serverpilot/apps/cryotshock/public/wp-config.php(82): require_once('/srv/users/serv...')
#3 /srv/users/serverpilot/apps/cryotshock/public/wp-load.php(37): require_once('/srv/users/serv...')
#4 /srv/users/serverpilot/apps/cryotshock/public/wp-blog-header.php(13): require_once('/srv/users/serv...')
#5 /srv/users/serverpilot/apps/cryotshock/public/index.php(20): require('/srv/users/serv...')
#6 {main}
  thrown in <b>/srv/users/serverpilot/apps/cryotshock/public/wp-includes/error-protection.php</b> on line <b>119</b><br />