?️ PHP filter_input() Function

? Quick Overview

The filter_input() function is used to fetch external input data and apply validation or sanitization in a single step. It is commonly used with form data, URLs, cookies, and server variables to improve application security.

? Key Concepts

• Fetches input from external sources
• Supports validation and sanitization
• Returns NULL for invalid input
• Helps prevent security vulnerabilities

? Syntax & Theory

Function Syntax:

// filter_input syntax structure
filter_input(int $type, string $variable_name, int $filter = FILTER_DEFAULT, mixed $options = null);

? Code Example

// Simulating GET request data
$_GET['email'] = "test@example.com";
$_GET['age'] = "25";

// Validate email input
$email = filter_input(INPUT_GET, 'email', FILTER_VALIDATE_EMAIL);
if ($email) {
echo "Valid Email: $email
";
} else {
echo "Invalid Email
";
}

// Validate integer input
$age = filter_input(INPUT_GET, 'age', FILTER_VALIDATE_INT);
if ($age) {
echo "Valid Age: $age
";
} else {
echo "Invalid Age
";
}

? Live Output / Explanation

• Email is checked using FILTER_VALIDATE_EMAIL
• Age is validated using FILTER_VALIDATE_INT
• Invalid inputs return NULL

? Interactive Insight

You can replace INPUT_GET with INPUT_POST and test the behavior using an HTML form submission.

? Use Cases

• Form input validation
• Secure login systems
• Filtering URL parameters
• Sanitizing user-submitted data