What are the potential pitfalls of not properly handling variable passing in PHP?

Not properly handling variable passing in PHP can lead to unexpected behavior and errors in your code. It is important to ensure that variables are passed correctly between functions or scopes to avoid issues such as undefined variables or unintended overwriting of values. To solve this, make sure to use proper variable scope and pass variables as arguments when calling functions.

// Incorrect way of passing variables
function addNumbers() {
    $sum = $num1 + $num2; // $num1 and $num2 are not defined in this function
    return $sum;
}

$num1 = 5;
$num2 = 10;
$result = addNumbers(); // This will result in an error

// Correct way of passing variables
function addNumbers($num1, $num2) {
    $sum = $num1 + $num2;
    return $sum;
}

$num1 = 5;
$num2 = 10;
$result = addNumbers($num1, $num2); // This will correctly pass the variables