What are the best practices for PHP function parameter validation?

PHP function parameter validation best practices include: explicitly declaring types and default values. Use built-in validation functions. Create a custom validation class. Use assertions. Following these practices ensures that PHP functions receive valid data and prevents unexpected crashes or incorrect results.

Best Practices for PHP Function Parameter Validation

When building functions in PHP, parameter validation is crucial, it can Ensure functions receive valid data to prevent unexpected crashes or incorrect results. Here are some best practices for validating function parameters:

Explicitly declare types and default values

Use type hints to explicitly declare the expected type of function parameters and make them optional Parameters specify default values. This helps the IDE detect errors and provide better code completion.

function calculateArea(float $length, float $width = 1): float
{
    return $length * $width;
}

Use built-in verification functions

PHP provides a rich set of built-in verification functions, such as is_int(), is_string( ), filter_var() etc. Parameter values ​​can be easily verified using these functions.

function validateEmail(string $email): bool
{
    return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
}

Custom validation class

For more complex validation requirements, you can create a custom validation class. This provides a centralized location to define and reuse validation rules.

class StringValidator
{
    public static function isAlpha(string $value): bool
    {
        return preg_match('/^[a-zA-Z]+$/', $value) === 1;
    }
}

Using assertions

PHP 7.0 introduced assertions, providing a concise and strict way to verify parameter values.

function updateBalance(int $amount): void
{
    assert($amount > 0, 'Amount must be positive');
    // 更新余额代码...
}

Practical Case

Let’s create a simple PHP function to validate and process form input:

function processForm(string $name, string $email, int $age = null): void
{
    // 验证 name
    if (empty($name)) {
        throw new Exception('Name cannot be empty');
    }

    // 验证 email
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        throw new Exception('Invalid email address');
    }

    // 验证 age（非必需）
    if ($age !== null && !is_numeric($age)) {
        throw new Exception('Age must be a number');
    }

    // 处理表单数据...
}

By following these best practices, You can write PHP functions that are robust and reliable, ensuring that they handle valid data and produce expected results.

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