The require_once() statement includes and
evaluates the specified file during the execution of the
script. This is a behavior similar to the require()
statement, with the only difference being that if the code
from a file has already been included, it will not be
included again. See the documentation for require()
for more information on how this statement works.
require_once() should be used in cases
where 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.
For examples on using
require_once() and
include_once(), look at the PEAR code included
in the latest PHP source code distributions.
注: require_once() was added in PHP 4.0.1pl2
注: Be aware, that the behaviour of require_once() and include_once() may not be what you expect on a non case sensitive operating system (such as Windows).
範例 12-8. require_once() is case sensitive
require_once("a.php"); // this will include a.php require_once("A.php"); // this will include a.php again on Windows!
|
See also: require(),
include(), include_once(),
get_required_files(),
get_included_files(),
readfile(), and virtual().