February 12, 2011 
Definition:
function map_meta_cap( $cap, $user_id ) {}
Map meta capabilities to primitive capabilities.
This does not actually compare whether the user ID has the actual capability, just what the capability or capabilities are. Meta capability list value can be ‘delete_user’, ‘edit_user’, ‘remove_user’, ‘promote_user’, ‘delete_post’, ‘delete_page’, ‘edit_post’, ‘edit_page’, ‘read_post’, or ‘read_page’.
Parameters
- string $cap: Capability name.
- int $user_id: User ID.
Return values
returns:Actual capabilities for meta capability.
Defined filters
- auth_post_meta_{$meta_key}
apply_filters( "auth_post_meta_{$meta_key}", false, $meta_key, $post->ID, $user_id, $cap, $caps )
Source code
function map_meta_cap( $cap, $user_id ) {
$args = array_slice( func_get_args(), 2 );
$caps = array();
switch ( $cap ) {
case 'remove_user':
$caps[] = 'remove_users';
break;
case 'promote_user':
$caps[] = 'promote_users';
break;
case 'edit_user':
// Allow user to edit itself
if ( isset( $args[0] ) && $user_id == $args[0] )
break;
// Fall through
case 'edit_users':
// If multisite these caps are allowed only for super admins.
if ( is_multisite() && !is_super_admin( $user_id ) )
$caps[] = 'do_not_allow';
else
$caps[] = 'edit_users'; // Explicit due to primitive fall through
break;
case 'delete_post':
case 'delete_page':
$author_data = get_userdata( $user_id );
$post = get_post( $args[0] );
if ( 'revision' == $post->post_type ) {
$post = get_post( $post->post_parent );
}
$post_type = get_post_type_object( $post->post_type );
if ( ! $post_type->map_meta_cap ) {
$caps[] = $post_type->cap->$cap;
// Prior to 3.1 we would re-call map_meta_cap here.
if ( 'delete_post' == $cap )
$cap = $post_type->cap->$cap;
break;
}
if ( '' != $post->post_author ) {
$post_author_data = get_userdata( $post->post_author );
} else {
// No author set yet, so default to current user for cap checks.
$post_author_data = $author_data;
}
// If the user is the author...
if ( is_object( $post_author_data ) && $user_id == $post_author_data->ID ) {
// If the post is published...
if ( 'publish' == $post->post_status ) {
$caps[] = $post_type->cap->delete_published_posts;
} elseif ( 'trash' == $post->post_status ) {
if ('publish' == get_post_meta($post->ID, '_wp_trash_meta_status', true) )
$caps[] = $post_type->cap->delete_published_posts;
} else {
// If the post is draft...
$caps[] = $post_type->cap->delete_posts;
}
} else {
// The user is trying to edit someone else's post.
$caps[] = $post_type->cap->delete_others_posts;
// The post is published, extra cap required.
if ( 'publish' == $post->post_status )
$caps[] = $post_type->cap->delete_published_posts;
elseif ( 'private' == $post->post_status )
$caps[] = $post_type->cap->delete_private_posts;
}
break;
// edit_post breaks down to edit_posts, edit_published_posts, or
// edit_others_posts
case 'edit_post':
case 'edit_page':
$author_data = get_userdata( $user_id );
$post = get_post( $args[0] );
if ( 'revision' == $post->post_type ) {
$post = get_post( $post->post_parent );
}
$post_type = get_post_type_object( $post->post_type );
if ( ! $post_type->map_meta_cap ) {
$caps[] = $post_type->cap->$cap;
// Prior to 3.1 we would re-call map_meta_cap here.
if ( 'edit_post' == $cap )
$cap = $post_type->cap->$cap;
break;
}
if ( '' != $post->post_author ) {
$post_author_data = get_userdata( $post->post_author );
} else {
// No author set yet, so default to current user for cap checks.
$post_author_data = $author_data;
}
//echo "current user id : $user_id, post author id: " . $post_author_data->ID . "<br />";
// If the user is the author...
if ( is_object( $post_author_data ) && $user_id == $post_author_data->ID ) {
// If the post is published...
if ( 'publish' == $post->post_status ) {
$caps[] = $post_type->cap->edit_published_posts;
} elseif ( 'trash' == $post->post_status ) {
if ('publish' == get_post_meta($post->ID, '_wp_trash_meta_status', true) )
$caps[] = $post_type->cap->edit_published_posts;
} else {
// If the post is draft...
$caps[] = $post_type->cap->edit_posts;
}
} else {
// The user is trying to edit someone else's post.
$caps[] = $post_type->cap->edit_others_posts;
// The post is published, extra cap required.
if ( 'publish' == $post->post_status )
$caps[] = $post_type->cap->edit_published_posts;
elseif ( 'private' == $post->post_status )
$caps[] = $post_type->cap->edit_private_posts;
}
break;
case 'read_post':
case 'read_page':
$author_data = get_userdata( $user_id );
$post = get_post( $args[0] );
if ( 'revision' == $post->post_type ) {
$post = get_post( $post->post_parent );
}
$post_type = get_post_type_object( $post->post_type );
if ( ! $post_type->map_meta_cap ) {
$caps[] = $post_type->cap->$cap;
// Prior to 3.1 we would re-call map_meta_cap here.
if ( 'read_post' == $cap )
$cap = $post_type->cap->$cap;
break;
}
if ( 'private' != $post->post_status ) {
$caps[] = $post_type->cap->read;
break;
}
if ( '' != $post->post_author ) {
$post_author_data = get_userdata( $post->post_author );
} else {
// No author set yet, so default to current user for cap checks.
$post_author_data = $author_data;
}
if ( is_object( $post_author_data ) && $user_id == $post_author_data->ID )
$caps[] = $post_type->cap->read;
else
$caps[] = $post_type->cap->read_private_posts;
break;
case 'edit_post_meta':
case 'delete_post_meta':
case 'add_post_meta':
$post = get_post( $args[0] );
$post_type_object = get_post_type_object( $post->post_type );
$caps = map_meta_cap( $post_type_object->cap->edit_post, $user_id, $post->ID );
$meta_key = isset( $args[ 1 ] ) ? $args[ 1 ] : false;
if ( $meta_key && has_filter( "auth_post_meta_{$meta_key}" ) ) {
$allowed = apply_filters( "auth_post_meta_{$meta_key}", false, $meta_key, $post->ID, $user_id, $cap, $caps );
if ( ! $allowed )
$caps[] = $cap;
} elseif ( $meta_key && is_protected_meta( $meta_key, 'post' ) ) {
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