How can variable scoping and naming conventions impact the functionality of PHP code?

Variable scoping and naming conventions can impact the functionality of PHP code by causing conflicts between variables with the same name in different scopes or by making the code harder to read and understand. To avoid these issues, it is important to follow best practices for variable naming conventions and to properly scope variables within functions or classes.

// Bad example with variable naming and scoping issues
$number = 5;

function multiplyNumber($number) {
    $result = $number * 2;
    return $result;
}

echo multiplyNumber($number); // Output: 10

// Good example with proper variable naming and scoping
$originalNumber = 5;

function multiplyNumber($inputNumber) {
    $result = $inputNumber * 2;
    return $result;
}

echo multiplyNumber($originalNumber); // Output: 10