This application uses Laravel.
First, modify composer.json as shown below to add a helper function.

"autoload": {
        "classmap": [
        "psr-4": {
            "App \\": "app /"
        "files": [
Applicable source code

Depending on the editor, a backslash is added at the beginning as shown below when calling a helper function.
By the way, it works even if there is no backslash.

\ helper_function ()

I would like to know when this backslash is necessary and useful.