include
include_once
Управляющие конструкции
PHP Manual

## require_once()

The require_once() statement is identical to require() except PHP will check if the file has already been included, and if so, not include (require) it again.

See the include_once() documentation for information about the _once behaviour, and how it differs from its non _once siblings.

include
include_once
Управляющие конструкции
PHP Manual