include_once()

This is a behavior similar to the include( ) statement , with the important difference that if the code from a file has already been included , it will not be included again .

As mentioned in the require_once( ) description , the include_once( ) should be used in the cases in which the same file might be included and evaluated more than once during a particular execution of a script , and you want to be sure that it is included exactly once to avoid problems with function redefinitions , variable value reassignments , etc .

include_once( ) was added in PHP 4.0.1pl2

See also : require( ) , include( ) , require_once( ) , get_required_files( ) , get_included_files( ) , readfile( ) , and virtual( ) .