PHP Form Validation Quiz

PHP Form Validation

• Form validation ensures form values are correct, preventing blank entries and ensuring data type matches (e.g., integers, real numbers, addresses, dates).
• It also checks if data fits the expected format and range of values.
• Validation is crucial for ensuring consistent and accurate data input from users.

Client-Side vs. Server-Side Validation

• Client-side validation happens before the form submission and can improve user experience. However, it is not secure.
• Server-side validation, using PHP code, takes place after submission, making the process secure—a necessary element for data security. Validating data before storing is important.
• A combination of both client and server-side validation provides a balance of usability and security. Server-side validation is needed for truly secure processes.

Useful Functions for Form Processing

• htmlspecialchars(): prevents injection of HTML or JavaScript. It encodes special characters to prevent exploitation.
• is_numeric(): validates if a variable holds a numeric value. This is essential for validating numerical input.
• isset(): checks if a variable is declared and initialized, validating the existence of a variable.
• empty(): determines if a variable is empty, validating for absence of input.
• $_SERVER["PHP_SELF"]: This special variable refers to the current script's filename. This function sends the submitted data back to the current page instead of redirecting to a different one.

Basic Server-Side Validation Code Example

• Extracts form data using $_REQUEST.
• Checks if the data matches required format and length, such as if the city/state/zip code is valid.
• Displays an error message if data is invalid and stops execution.

Advanced Validation Considerations

• Validation logic can be complex, requiring substantial coding.
• Examples include testing for integers, decimals, strings, credit card numbers, names with middle initials, and complex formats.
• Examples include validating for integers, decimals, strings, credit card numbers, names with middle initials, and other complex formats.

Validating Numeric Values

• Checks if variables 'height' and 'weight' are set.
• Validates if input values are numeric.
• Calculates BodyMass index using these values if valid. An error message is displayed upon invalid input.

filter_var() Function

• filter_var() is used to validate data types like integers, floating-point numbers, email addresses, URLs.
• This is a powerful function for web developers to validate and sanitize user input, reducing vulnerabilities.

FILTER_VALIDATE_*

• FILTER_VALIDATE_EMAIL: validates email address format.
• FILTER_VALIDATE_URL: validates URL format.