What are the drawbacks of using global variables in PHP functions, as mentioned in the forum thread?

Using global variables in PHP functions can lead to code that is harder to maintain, debug, and test. It can also introduce unexpected side effects and make the code less reusable. To solve this issue, it's better to pass variables as parameters to the function instead of relying on global variables.

// Avoid using global variables in PHP functions
$globalVar = 10;

function badFunction() {
    global $globalVar;
    return $globalVar * 2;
}

echo badFunction(); // Output: 20

// Refactor the function to accept parameters instead
function goodFunction($var) {
    return $var * 2;
}

echo goodFunction($globalVar); // Output: 20