How can PHP developers optimize their code to prevent issues with variable scope and data retrieval?

PHP developers can optimize their code by properly scoping variables and ensuring data retrieval is efficient. To prevent issues with variable scope, developers should use appropriate variable declarations within functions and classes to avoid conflicts with global variables. Additionally, developers can optimize data retrieval by minimizing unnecessary database queries and utilizing caching mechanisms to store frequently accessed data.

// Example of scoping variables properly within a function
function calculateSum($num1, $num2) {
    $sum = $num1 + $num2;
    return $sum;
}

// Example of optimizing data retrieval by caching frequently accessed data
function getProducts() {
    if(!isset($products)) {
        $products = // retrieve products from database
        // store products in cache
    }
    return $products;
}