wp-includes/class-wp-query.php:4192Determines whether the query is for an existing attachment page.
$attachmentint|string|int[]|string[]optional''bool public function is_attachment( $attachment = '' ) { if ( ! $this->is_attachment ) { return false; } if ( empty( $attachment ) ) { return true; } $attachment = array_map( 'strval', (array) $attachment ); $post_obj = $this->get_queried_object(); if ( ! $post_obj ) { return false; } if ( in_array( (string) $post_obj->ID, $attachment, true ) ) { return true; } elseif ( in_array( $post_obj->post_title, $attachment, true ) ) { return true; } elseif ( in_array( $post_obj->post_name, $attachment, true ) ) { return true; } return false; }Introduced in 3.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-query.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.