wp-includes/post.php:6606Determines whether an attachment URI is local and really an attachment.
$urlstringboolfunction is_local_attachment( $url ) { if ( ! str_contains( $url, home_url() ) ) { return false; } if ( str_contains( $url, home_url( '/?attachment_id=' ) ) ) { return true; } $id = url_to_postid( $url ); if ( $id ) { $post = get_post( $id ); if ( 'attachment' === $post->post_type ) { return true; } } return false;}Introduced in 2.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/post.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.