wp-includes/class-wp-rewrite.php:366Determines whether permalinks are being used and rewrite module is not enabled.
bool public function using_index_permalinks() { if ( empty( $this->permalink_structure ) ) { return false; } // If the index is not in the permalink, we're using mod_rewrite. return preg_match( '#^/*' . $this->index . '#', $this->permalink_structure ); }Introduced in 1.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-rewrite.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.