How do you make a variable available within all scopes in PHP?

Making a variable available within all scopes in PHP is done by declaring it as a global variable using the global keyword. In PHP, variables typically exist within a specific scope, such as local (inside a function) or global (outside of functions). When you want to access a global variable inside a function, you must declare it as global within that function.

Using the global keyword allows you to link the variable declared in the global scope to the local function scope, meaning you can read or modify the global variable within the function. This is particularly useful when you need to use shared state across different functions without passing the variable around as a parameter.

Declaring a variable as local confines its visibility and accessibility solely to the function in which it is declared, making it unsuitable for use in all scopes. Likewise, declaring a variable as static retains its value between function calls but does not make it available globally. Declaring a variable as a constant means it cannot be changed and is not treated as a regular variable, thus it does not provide the desired functionality for variable scope sharing.