In what ways can PHP developers improve their understanding of variable types and function expectations to enhance code efficiency and readability?

PHP developers can improve their understanding of variable types and function expectations by utilizing type declarations in function parameters and return types. This helps to enforce the expected types of arguments and return values, making the code more predictable and easier to understand. Additionally, documenting the expected types in function comments can also enhance code readability.

// Using type declarations in function parameters and return types
function calculateSum(int $num1, int $num2): int {
    return $num1 + $num2;
}

// Documenting the expected types in function comments
/**
 * Calculates the sum of two numbers.
 *
 * @param int $num1 The first number
 * @param int $num2 The second number
 * @return int The sum of the two numbers
 */
function calculateSum(int $num1, int $num2): int {
    return $num1 + $num2;
}