The include() statement includes and evaluates the specified file.

The documentation below also applies to require(). The two constructs are identical in every way except how they handle failure. include() produces a Warning while require() results in a Fatal Error. In other words, use require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. Be sure to have an appropriate include_path setting as well.

Dave_L wrote:
In addition, it's usually preferable to use include_once or require_once in place of include or require.