WordPress at a glance
filter is not described

is_protected_meta filter-hook . WP 3.2.0

Filters whether a meta key is protected.

Usage

add_filter( 'is_protected_meta', 'filter_function_name_8861', 10, 3 );
function filter_function_name_8861( $protected, $meta_key, $meta_type ){
	// filter...

	return $protected;
}
$protected(true/false)
Whether the key is protected.
Default: false
$meta_key(string)
Meta key.
$meta_type(string)
Type of object metadata is for (e.g., comment, post, term, or user).

Where the hook is called

is_protected_meta()
wp-includes/meta.php 1008
return apply_filters( 'is_protected_meta', $protected, $meta_key, $meta_type );

Where the hook is used (in WP core)

Does not used.