Pages in php call each other

Require () and require_once (): the same file is called only once and is usually placed at the beginning of the PHP program. before the PHP program is executed, read the file specified by require first. If an error occurs, it is fatal. Include () and include_once (): the same file is called only once... require () and require_once ()

Require_once (): the same file is called only once.

Usually put at the beginning of the PHP program. before the PHP program is executed, it will first read require

If an error occurs in the specified imported file, it is fatal.

Include () and include_once ()

Include_once ()
: The same file is called only once.

It can be placed in any position of the PHP program. The PHP program will read

If an error occurs, the system will prompt the file imported by include.