What is the usage of include_once in PHP?

The statement include_once is used in PHP to include a file.

Its usage is as follows:

Use the “文件路径” file just once.

The file path can be either a relative path or an absolute path.

The include_once function will include a specified file into the current PHP script. If the file has already been included before, it will be skipped to avoid errors caused by duplicate definitions.

Unlike “include,” “include_once” checks the file to ensure it is only included once. This is useful when including the same file multiple times to prevent errors caused by duplicate definitions.

Note: When using include_once to include a file, a warning will be issued if the file does not exist or the path is incorrect, but it will not cause the script to stop executing.