How are input validation and data filtering handled in PHP functions?

Input validation and data filtering in PHP functions are critical to protecting application security. They include: Input validation: verify data type, length, mode, etc. Data filtering: escape characters, remove HTML tags, encryption. Usage Example: PHP function processes user form data using filters and validation.

Implementing input validation and data filtering in PHP functions

Introduction

Input validation and data filtering are critical to protecting web applications from malicious input. PHP provides a variety of mechanisms to accomplish these tasks and ensure that user input is safe and reliable.

Input Validation

Input validation checks whether user input is legal and as expected. Common validation techniques include:

• Type checking: ensuring that the input is of a specific data type, such as a string or a number.
• Length check: Verify that the input length is within the predefined range.
• Regular Expressions: Use regular expressions to match patterns, such as email addresses or phone numbers.

Data filtering

Data filtering removes or modifies harmful characters or codes in user input. Common filtering techniques include:

• Escape characters: Escape special characters (such as quotes) so that they are not interpreted by the code.
• Remove HTML tags: Remove HTML tags from input to prevent cross-site scripting attacks (XSS).
• Encryption: Convert sensitive information into an unreadable format to prevent unauthorized access.

Practical case

The following PHP function uses filters and validation to process form data submitted by users:

function validate_and_filter_input(array $data): array
{
    // 输入验证
    if (!isset($data['username']) || empty($data['username'])) {
        throw new InvalidArgumentException("Missing or empty username");
    }
    if (!ctype_alpha($data['username'])) {
        throw new InvalidArgumentException("Username must only contain alphabetic characters");
    }
    if (strlen($data['username']) > 20) {
        throw new InvalidArgumentException("Username must be less than 20 characters long");
    }
    if (!filter_var($data['email'], FILTER_VALIDATE_EMAIL)) {
        throw new InvalidArgumentException("Invalid email address");
    }

    // 数据过滤
    $data['username'] = htmlspecialchars($data['username']);
    $data['email'] = filter_var($data['email'], FILTER_SANITIZE_EMAIL);

    return $data;
}

Conclusion

Input validation and data filtering are critical to ensuring the security and reliability of PHP applications. By leveraging the mechanisms provided by PHP, you can efficiently handle user input and protect your application from malicious attacks.

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