What are the potential pitfalls of implementing self-validation based on type in PHP?

One potential pitfall of implementing self-validation based on type in PHP is that it can lead to unexpected behavior if the type of a variable changes during runtime. To solve this issue, you can use strict type declarations in PHP to ensure that variables maintain their specified types throughout the execution of the script.

declare(strict_types=1);

function validateString(string $input): bool {
    // Validation logic for string input
    return true;
}

// Example usage
$input = "Hello";
if (validateString($input)) {
    echo "Input is valid";
} else {
    echo "Input is invalid";
}