Why is type checking important in PHP, and how can it be implemented effectively?

Type checking is important in PHP to ensure that variables are of the correct type before performing operations on them, preventing unexpected errors or behavior. This can be implemented effectively by using type declarations in function parameters or return types, as well as using the `is_*` functions to check the type of variables.

function calculate(int $num1, int $num2): int {
    return $num1 + $num2;
}

$num1 = 5;
$num2 = "10";

if (is_int($num1) && is_int($num2)) {
    echo calculate($num1, $num2);
} else {
    echo "Invalid input. Numbers must be integers.";
}