PHP » Control Structures » require_once()

mixed require_once(string filepath)
The path to the file that is to be called.

Calls an external script to execute, if it has not already been called.

require_once() is very similar to require(), but is used when there is a risk that including a file more than once will lead to conflicts. This function guarantees that a file is not included more than once during the same execution of a script.

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