What best practices should be followed when designing PHP scripts to prevent errors related to variable scope and ensure smooth execution of code?

When designing PHP scripts, it is important to properly manage variable scope to prevent errors and ensure smooth execution of code. One best practice is to use the `global` keyword sparingly and instead pass variables as parameters to functions when needed. Additionally, utilizing PHP's built-in functions like `isset()` and `empty()` can help avoid undefined variable errors.

// Example of properly managing variable scope in PHP scripts
$globalVariable = "I am a global variable";

function myFunction($parameter) {
    echo $parameter;
}

myFunction($globalVariable);