wp-includes/functions.php:2162Joins two filesystem paths together.
$basestring$pathstringstringfunction path_join( $base, $path ) { if ( path_is_absolute( $path ) ) { return $path; } return rtrim( $base, '/' ) . '/' . $path;}Introduced in 2.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.