wp-includes/class-wp-query.php:4127Determines whether the query is for an existing author archive page.
$authorint|string|int[]|string[]optional''bool public function is_author( $author = '' ) { if ( ! $this->is_author ) { return false; } if ( empty( $author ) ) { return true; } $author_obj = $this->get_queried_object(); if ( ! $author_obj ) { return false; } $author = array_map( 'strval', (array) $author ); if ( in_array( (string) $author_obj->ID, $author, true ) ) { return true; } elseif ( in_array( $author_obj->nickname, $author, true ) ) { return true; } elseif ( in_array( $author_obj->user_nicename, $author, 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.