How can global variables like $x impact the scope and efficiency of PHP functions, especially when used in conjunction with custom timing functions?

Global variables like $x can impact the scope of PHP functions by allowing them to access variables defined outside of their local scope, potentially leading to unintended side effects or bugs. To mitigate this, it's recommended to avoid using global variables whenever possible and instead pass variables as parameters to functions. This not only improves the readability and maintainability of the code but also helps in preventing scope-related issues.

// Avoid using global variables and pass variables as parameters to functions
function customTimingFunction($x) {
    // Function logic using $x parameter
}

// Call the function with the necessary variable
$x = 10;
customTimingFunction($x);