How to use the require_once statement in PHP?

@denis 

In PHP, the require_once statement is used to include a file in the current PHP script. The difference between require_once and require is that require_once will check if the file has already been included and, if so, will not include it again, while require will include the file every time it is called.

The syntax for using require_once is:

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require_once "path/to/file.php";

Here, "path/to/file.php" is the path to the file you want to include in your script. This path can be relative to the current script or an absolute path.

For example, let's say you have a file called functions.php that contains some useful functions you want to use in your current script. To include this file using require_once, you would use the following code:

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require_once "functions.php";

Once this line of code is executed, the contents of the functions.php file will be available to your current script, allowing you to call any of the functions defined in that file.

It's important to note that if the file specified in require_once cannot be found, a fatal error will be generated and the script will stop executing. So, make sure that you have the correct path to the file and that the file actually exists before using require_once.