How to check variable is declared or not in Laravel to avoid an Error.

Suppose we have not declared a variable in the controller and calling it in views, then it shows undefined variable Error. See the below image.

Suppose, we are calling $string variable and we have not declared the variable in the controller so it gives an error like above shown.
To avoid this error we use @isset function. See the below image for code.

as we have not declared the string so it returns Variable is not found. See the below image.