include_once
The include_once
expression includes and evaluates
the specified file during the execution of the script.
This is a behavior similar to the include expression,
with the only difference being that if the code from a file has already
been included, it will not be included again, and include_once returns true
. As the name suggests,
the file will be included just once.
include_once
may be used in cases where
the same file might be included and evaluated more than once during a
particular execution of a script, so in this case it may help avoid
problems such as function redefinitions, variable value reassignments, etc.
See the include documentation for information about
how this function works.